[usth/ICT2.2] Object Oriented Programming

125 files changed, 3793 insertions, 15 deletions

diff --git a/README.md b/README.md
index 393c47a..4ebe2ae 100644
--- a/README.md
+++ b/README.md
@@ -2,21 +2,22 @@
 
 Bài tập luyện tập thi Olympic, học sinh giỏi Tin học, trong đó:
 
-|         Thư mục        |                   Nguồn đề bài                    |
-| ---------------------- | ------------------------------------------------- |
-| `09`, `10`, `11`, `12` | Đề thi, kiểm tra phân theo lớp                    |
-| `COCI`                 | [Giải Tin học Croatia mở rộng][0]                 |
-| `NTU`                  | [Đại học Nha Trang][1]                            |
-| `THT`                  | Hội thi Tin học trẻ                               |
-| `codechef`             | [Codechef][2]                                     |
-| `codeforces`           | [Codeforces][3]                                   |
-| `cpptour`              | A Tour of C++                                     |
-| `daily`                | [/r/dailyprogrammer][4]                           |
-| `others`               | Các đề bài không rõ nguồn                         |
-| `paip`                 | Paradigms of Artificial Intelligence Programming  |
-| `sicp`                 | Structure and Interpretation of Computer Programs |
-| `thinkperl6`           | Think Perl 6                                      |
-| `toys`                 | Programs that don't deserve their own repo        |
+|    Thư mục   |                      Nguồn đề bài                      |
+| ------------ | ------------------------------------------------------ |
+| `\d{2}`      | Đề thi, kiểm tra phân theo lớp                         |
+| `COCI`       | [Giải Tin học Croatia mở rộng][0]                      |
+| `NTU`        | [Đại học Nha Trang][1]                                 |
+| `THT`        | Hội thi Tin học trẻ                                    |
+| `codechef`   | [Codechef][2]                                          |
+| `codeforces` | [Codeforces][3]                                        |
+| `cpptour`    | A Tour of C++                                          |
+| `daily`      | [/r/dailyprogrammer][4]                                |
+| `others`     | Các đề bài không rõ nguồn                              |
+| `paip`       | Paradigms of Artificial Intelligence Programming       |
+| `sicp`       | Structure and Interpretation of Computer Programs      |
+| `thinkperl6` | Think Perl 6                                           |
+| `toys`       | Programs that don't deserve their own repo             |
+| `usth`       | L'Université des Sciences et des Technologies de Hanoï |
 
 [0]: http://www.hsin.hr/coci/
 [1]: http://laptrinh.ntu.edu.vn/
@@ -34,6 +35,7 @@ Phiên bản các trình dịch sử dụng test:
 | ----------- | ------------------ |
 | C           | GNU GCC 4.9+       |
 | Common Lisp | SBCL 1.4.8+        |
+| Java        | OpenJDK 11+        |
 | Lua         | Lua 5.1+           |
 | Pascal      | Free Pascal 2.6.4+ |
 | Perl 6      | Rakudo 2018.12+    |
diff --git a/usth/ICT2.2/final/Member.java b/usth/ICT2.2/final/Member.java
new file mode 100644
index 0000000..a3e2092
--- /dev/null
+++ b/usth/ICT2.2/final/Member.java
@@ -0,0 +1,54 @@
+public class Member
+{
+  public static final String[] ROLES = {"leader", "club coordinator",
+                                        "keynote speaker of code sharing",
+                                        "product programmer"};
+
+  private String name;
+  private String time;
+  private int role;
+
+  public String getName()
+  {
+    return name;
+  }
+
+  public String getTime()
+  {
+    return time;
+  }
+
+  public int getRole()
+  {
+    return role;
+  }
+  
+  public void setName(String name)
+  {
+    this.name = name;
+  }
+  
+  public void setTime(String time)
+  {
+    this.time = time;
+  }
+  
+  public void setRole(int role) throws IllegalArgumentException
+  {
+    if (role < 0 || role > 3)
+      throw new IllegalArgumentException("invalid role number: " + role);
+    this.role = role;
+  }
+
+  public Member(String name, String time, int role)
+  {
+    setName(name);
+    setTime(time);
+    setRole(role);
+  }
+
+  public String toString()
+  {
+    return String.format("%s (%s), from %s", name, ROLES[role], time);
+  }
+}
diff --git a/usth/ICT2.2/final/Point.java b/usth/ICT2.2/final/Point.java
new file mode 100644
index 0000000..5e79428
--- /dev/null
+++ b/usth/ICT2.2/final/Point.java
@@ -0,0 +1,43 @@
+// Immutable Point
+public class Point
+{
+  private double x;
+  private double y;
+
+  public Point(double x, double y)
+  {
+    this.x = x;
+    this.y = y;
+  }
+
+  public double getX()
+  {
+    return x;
+  }
+
+  public double getY()
+  {
+    return y;
+  }
+
+  public String toString()
+  {
+    return String.format("(%g, %g)", x, y);
+  }
+
+  public static Point add(Point a, Point b)
+  {
+    return new Point(a.getX() + b.getX(), a.getY() + b.getY());
+  }
+
+  public static Point subtract(Point a, Point b)
+  {
+    return new Point(a.getX() - b.getX(), a.getY() - b.getY());
+  }
+
+  public static double calDisEuclid(Point a, Point b)
+  {
+    var trans = Point.subtract(a, b);
+    return Math.sqrt(trans.getX()*trans.getX() + trans.getY()*trans.getY());
+  }
+}
diff --git a/usth/ICT2.2/final/Problem1.java b/usth/ICT2.2/final/Problem1.java
new file mode 100644
index 0000000..a9c5e32
--- /dev/null
+++ b/usth/ICT2.2/final/Problem1.java
@@ -0,0 +1,15 @@
+import java.util.Scanner;
+
+class Problem1
+{
+  public static void main(String... args)
+  {
+    var scanner = new Scanner(System.in);
+    int n = scanner.nextInt();
+    for (int i = 1; i <= n; i += 2)
+      System.out.println(i);
+    if (n % 2 == 0)
+      n--;
+    System.out.println((n + 1) * (n + 1) / 4);
+  }
+}
diff --git a/usth/ICT2.2/final/Problem2.java b/usth/ICT2.2/final/Problem2.java
new file mode 100644
index 0000000..dcad796
--- /dev/null
+++ b/usth/ICT2.2/final/Problem2.java
@@ -0,0 +1,22 @@
+import java.util.Scanner;
+
+class Problem2
+{
+  public static void main(String... args)
+  {
+    var scanner = new Scanner(System.in);
+    System.out.println(
+        "Please enter two numbers which are the coordinate of one point:");
+    var a = new Point(scanner.nextDouble(), scanner.nextDouble());
+    System.out.println(
+        "Please enter two numbers which are the coordinate of another point:");
+    var b = new Point(scanner.nextDouble(), scanner.nextDouble());
+
+    System.out.printf("First point: %s\nSecond point: %s\n", a, b);
+    // Vector would make a better name than Point
+    System.out.printf("Their sum: %s\nTheir difference: %s\n",
+                      Point.add(a, b), Point.subtract(a, b));
+    System.out.printf("The Euclidean distance between the two points: %s\n",
+                      Point.calDisEuclid(a, b));
+  }
+}
diff --git a/usth/ICT2.2/final/Problem3.java b/usth/ICT2.2/final/Problem3.java
new file mode 100644
index 0000000..11be143
--- /dev/null
+++ b/usth/ICT2.2/final/Problem3.java
@@ -0,0 +1,40 @@
+import java.util.ArrayList;
+import java.util.Scanner;
+
+class Problem3
+{
+  public static void main(String... args)
+  {
+    var scanner = new Scanner(System.in);
+    System.out.println("Number of members:");
+    int n = scanner.nextInt();
+
+    var members = new ArrayList<Member>();
+    for (int i = 0; i < n; ++i)
+      {
+        System.out.println("Member name: ");
+        String name = scanner.next();
+        System.out.println("Member joining time: ");
+        String time = scanner.next();
+        System.out.println("Member role number: ");
+        int role = scanner.nextInt();
+        members.add(new Member(name, time, role));
+      }
+
+    var reports = new ArrayList<Report>();
+    for (var m : members)
+      {
+        System.out.println(m);
+        System.out.println("Activity: ");
+        String act = scanner.next();
+        System.out.println("Rate: ");
+        int rate = scanner.nextInt();
+        reports.add(new Report(m.getName(), act, rate));
+      }
+
+    System.out.println("Members:");
+    members.forEach(System.out::println);
+    System.out.println("Activity reports:");
+    reports.forEach(System.out::println);
+  }
+}
diff --git a/usth/ICT2.2/final/Report.java b/usth/ICT2.2/final/Report.java
new file mode 100644
index 0000000..ec4ee23
--- /dev/null
+++ b/usth/ICT2.2/final/Report.java
@@ -0,0 +1,18 @@
+public class Report
+{
+  String name;
+  String activity;
+  int rate;
+
+  public Report(String name, String act, int rate)
+  {
+    this.name = name;
+    this.activity = act;
+    this.rate = rate;
+  }
+
+  public String toString()
+  {
+    return String.format("%s: %s: %s", name, activity, rate);
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/AllEqual.java b/usth/ICT2.2/labwork/1/AllEqual.java
new file mode 100644
index 0000000..b1d6929
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/AllEqual.java
@@ -0,0 +1,10 @@
+import java.util.Arrays;
+
+class AllEqual
+{
+  public static void main(String... args)
+  {
+    String first = args[0];
+    System.out.println(Arrays.stream(args).allMatch(a -> (a.equals(first))));
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/Binary.java b/usth/ICT2.2/labwork/1/Binary.java
new file mode 100644
index 0000000..3573a35
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/Binary.java
@@ -0,0 +1,14 @@
+class Binary
+{
+  public static void main(String... args)
+  {
+    int n = Integer.parseInt(args[0]);
+    String s = "";
+    while (n > 0)
+      {
+        s = (n % 2) + s;
+        n >>= 1;
+      }
+    System.out.println(s);
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/Distance.java b/usth/ICT2.2/labwork/1/Distance.java
new file mode 100644
index 0000000..16bcc2c
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/Distance.java
@@ -0,0 +1,10 @@
+class Distance
+{
+  public static void main(String... args)
+  {
+    double x = Double.parseDouble(args[0]);
+    double y = Double.parseDouble(args[1]);
+    System.out.printf("The distance from (%g, %g) to origin is %g\n",
+                      x, y, Math.sqrt(x*x + y*y));
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/FivePerLine.java b/usth/ICT2.2/labwork/1/FivePerLine.java
new file mode 100644
index 0000000..339e6cf
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/FivePerLine.java
@@ -0,0 +1,11 @@
+class FivePerLine
+{
+  public static void main(String... args)
+  {
+    for (int i = 1000; i < 2000; ++i)
+      if (i % 5 < 4)
+        System.out.print(i + " ");
+      else
+        System.out.println(i);
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/FunctionGrowth.java b/usth/ICT2.2/labwork/1/FunctionGrowth.java
new file mode 100644
index 0000000..e1bebfa
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/FunctionGrowth.java
@@ -0,0 +1,10 @@
+class FunctionGrowth
+{
+  public static void main(String... args)
+  {
+    System.out.println("ln n\tn\tn ln n\tn^2\tn^3\t2^n");
+    for (long n = 16; n < 3005; n <<= 1)
+      System.out.printf("%g\t%d\t%g\t%d\t%d\t%g\n", Math.log(n), n,
+                        n * Math.log(n), n*n, n*n*n, Math.pow(2, n));
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/HelloWorld.java b/usth/ICT2.2/labwork/1/HelloWorld.java
new file mode 100644
index 0000000..cf7313a
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/HelloWorld.java
@@ -0,0 +1,7 @@
+class HelloWorld
+{
+  public static void main(String... args)
+  {
+    System.out.println("Hello, World!");
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/Hellos.java b/usth/ICT2.2/labwork/1/Hellos.java
new file mode 100644
index 0000000..206ac58
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/Hellos.java
@@ -0,0 +1,14 @@
+class Hellos
+{
+  private static final String[] TH = {"th", "st", "nd", "rd", "th",
+                                      "th", "th", "th", "th", "th"};
+
+  public static void main(String... args)
+  {
+    int n = Integer.parseInt(args[0]);
+    for (int i = 1; i <= n; ++i)
+      // Before one says this defeat the purpose of the section,
+      // the tertiary operator IS conditional.
+      System.out.println(i + TH[i % 100 / 10 == 1 ? 7 : i % 10] + " Hello");
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/Kary.java b/usth/ICT2.2/labwork/1/Kary.java
new file mode 100644
index 0000000..51fd9af
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/Kary.java
@@ -0,0 +1,22 @@
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+class Kary
+{ 
+  private static final char[] DIGITS = {'0', '1', '2', '3', '4', '5', '6', '7',
+                                        '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
+
+  public static void main(String... args)
+  { 
+    int n = Integer.parseInt(args[0]);
+    List<Character> result = new ArrayList<Character>();
+    for (int k = Integer.parseInt(args[1]); n > 0; n /= k)
+      result.add(DIGITS[n % k]);
+
+    Collections.reverse(result);
+    for (char d : result)
+      System.out.print(d);
+    System.out.println();
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/RollLoadedDie.java b/usth/ICT2.2/labwork/1/RollLoadedDie.java
new file mode 100644
index 0000000..161fd93
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/RollLoadedDie.java
@@ -0,0 +1,10 @@
+import java.util.concurrent.ThreadLocalRandom;
+
+class RollLoadedDie
+{
+  public static void main(String... args)
+  {
+    int x = ThreadLocalRandom.current().nextInt(1, 9);
+    System.out.println((x < 6) ? x : 6);
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/SpringSeason.java b/usth/ICT2.2/labwork/1/SpringSeason.java
new file mode 100644
index 0000000..2fda09b
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/SpringSeason.java
@@ -0,0 +1,25 @@
+import java.time.LocalDate;
+import java.time.DateTimeException;
+
+class SpringSeason
+{
+  private static final LocalDate start = LocalDate.of(42, 3, 19);
+  private static final LocalDate end = LocalDate.of(42, 6, 21);
+
+  public static void main(String... args)
+  {
+    int m = Integer.parseInt(args[0]);
+    int d = Integer.parseInt(args[1]);
+    try
+      {
+        LocalDate query = LocalDate.of(42, m, d);
+        // Yes, I'm sorry for leaving it here.
+        // If only Java has the try-except-else like Python!
+        System.out.println(query.isAfter(start) && query.isBefore(end));
+      }
+    catch (DateTimeException e)
+      {
+        System.out.println(false);
+      }
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/SumOfSines.java b/usth/ICT2.2/labwork/1/SumOfSines.java
new file mode 100644
index 0000000..2cf6e03
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/SumOfSines.java
@@ -0,0 +1,8 @@
+class SumOfSines
+{
+  public static void main(String... args)
+  {
+    double t = Double.parseDouble(args[0]);
+    System.out.printf("sin2t + sin3t = %g", Math.sin(t * 2) + Math.sin (t * 3));
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/SumOfTwoDice.java b/usth/ICT2.2/labwork/1/SumOfTwoDice.java
new file mode 100644
index 0000000..d955f28
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/SumOfTwoDice.java
@@ -0,0 +1,13 @@
+import java.util.concurrent.ThreadLocalRandom;
+
+class SumOfTwoDice
+{
+  public static void main(String... args)
+  {
+    int x = ThreadLocalRandom.current().nextInt(1, 7);
+    System.out.println("First roll: " + x);
+    int y = ThreadLocalRandom.current().nextInt(1, 7);
+    System.out.println("Second roll: " + y);
+    System.out.println("Sum: " + (x + y));
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/TenHelloWorld.java b/usth/ICT2.2/labwork/1/TenHelloWorld.java
new file mode 100644
index 0000000..d8a2cd9
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/TenHelloWorld.java
@@ -0,0 +1,8 @@
+class TenHelloWorld
+{
+  public static void main(String... args)
+  {
+    for (int i = 0; i < 10; ++i)
+      System.out.println("Hello, World!");
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/UseArguments.java b/usth/ICT2.2/labwork/1/UseArguments.java
new file mode 100644
index 0000000..d477f51
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/UseArguments.java
@@ -0,0 +1,7 @@
+class UseArguments
+{
+  public static void main(String... args)
+  {
+    System.out.printf("Hi %s.  How are you?\n", args[0]);
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/UseThree.java b/usth/ICT2.2/labwork/1/UseThree.java
new file mode 100644
index 0000000..9b5693b
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/UseThree.java
@@ -0,0 +1,8 @@
+class UseThree
+{
+  public static void main(String... args)
+  {
+    System.out.printf("Hi %s, %s and %s.  How are you?\n",
+                      args[2], args[1], args[0]);
+  }
+}
diff --git a/usth/ICT2.2/labwork/1/logic-xor-table.md b/usth/ICT2.2/labwork/1/logic-xor-table.md
new file mode 100644
index 0000000..e955d5b
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/logic-xor-table.md
@@ -0,0 +1,8 @@
+# Logical Exclusive Or Table
+
+|   a   |   b   | a ^ b |
+| ----- | ----- | ----- |
+| false | false | false |
+| false | true  | true  |
+| true  | false | true  |
+| true  | true  | false |
diff --git a/usth/ICT2.2/labwork/1/string-concat.md b/usth/ICT2.2/labwork/1/string-concat.md
new file mode 100644
index 0000000..624383f
--- /dev/null
+++ b/usth/ICT2.2/labwork/1/string-concat.md
@@ -0,0 +1,15 @@
+# String Concatenation
+
+To quote the [official Java documentation](https://docs.oracle.com/javase/8/docs/api/java/lang/String.html):
+
+> The Java language provides special support for the string concatenation
+> operator (`+`), and for conversion of other objects to strings.  [...]
+> String conversions are implemented through the method `toString`, defined
+> by Object and inherited by all classes in Java.
+
+Thus the numbers (e.g. 2, 2 + 3 = 5) are converted to their strings
+representations ("2", "5") and concatenated to the string.  Since `+` is
+operated from left to right,
+
+    2 + 3 + "bc" = 5 + "bc" = "5" + "bc" = "5bc"
+    "bc" + 2 + 3 = "bc" + "2" + 3 = "bc2" + 3 = "bc2" + "3" = "bc23"
diff --git a/usth/ICT2.2/labwork/2/1_labwork1-extra.pdf b/usth/ICT2.2/labwork/2/1_labwork1-extra.pdf
new file mode 100644
index 0000000..278400a
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/1_labwork1-extra.pdf
Binary files differdiff --git a/usth/ICT2.2/labwork/2/2_labwork2.pdf b/usth/ICT2.2/labwork/2/2_labwork2.pdf
new file mode 100644
index 0000000..3cd1908
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/2_labwork2.pdf
Binary files differdiff --git a/usth/ICT2.2/labwork/2/README.md b/usth/ICT2.2/labwork/2/README.md
new file mode 100644
index 0000000..a81631e
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/README.md
@@ -0,0 +1,18 @@
+# Build with Maven
+
+Following the official guide [Maven in 5 Minutes](https://maven.apache.org/guides/getting-started/maven-in-five-minutes.html):
+
+1. Create a project named `my-app`:
+
+        mvn archetype:generate -DgroupId=com.mycompany.app -DartifactId=my-app -DarchetypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.4 -DinteractiveMode=false
+
+2. Change into the project directory: `cd my-app`
+3. Build the project: `mvn package`
+
+Extra exercises for labwork 1 are written in `src/main/java/com/mycompany/app/`
+inside `my-app`.  To launch a class named `App` for example, run
+
+    java -cp my-app/target/my-app-1.0-SNAPSHOT.jar com.mycompany.app.App
+
+I find this build method to be overcomplicated for 5-minute throw-away programs
+and decide not to use it in the upcoming labworks.
diff --git a/usth/ICT2.2/labwork/2/my-app/pom.xml b/usth/ICT2.2/labwork/2/my-app/pom.xml
new file mode 100644
index 0000000..07012c1
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/pom.xml
@@ -0,0 +1,75 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>com.mycompany.app</groupId>
+  <artifactId>my-app</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <name>my-app</name>
+  <!-- FIXME change it to the project's website -->
+  <url>http://www.example.com</url>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <maven.compiler.source>1.8</maven.compiler.source>
+    <maven.compiler.target>1.8</maven.compiler.target>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.11</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
+      <plugins>
+        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
+        <plugin>
+          <artifactId>maven-clean-plugin</artifactId>
+          <version>3.1.0</version>
+        </plugin>
+        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
+        <plugin>
+          <artifactId>maven-resources-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-compiler-plugin</artifactId>
+          <version>3.8.0</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-surefire-plugin</artifactId>
+          <version>2.22.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-jar-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-install-plugin</artifactId>
+          <version>2.5.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-deploy-plugin</artifactId>
+          <version>2.8.2</version>
+        </plugin>
+        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
+        <plugin>
+          <artifactId>maven-site-plugin</artifactId>
+          <version>3.7.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-project-info-reports-plugin</artifactId>
+          <version>3.0.0</version>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+  </build>
+</project>
diff --git a/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/App.java b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/App.java
new file mode 100644
index 0000000..0f661cb
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/App.java
@@ -0,0 +1,9 @@
+package com.mycompany.app;
+
+public class App
+{
+  public static void main(String... args)
+  {
+    System.out.println("Hello World!");
+  }
+}
diff --git a/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Beers.java b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Beers.java
new file mode 100644
index 0000000..b74a93b
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Beers.java
@@ -0,0 +1,17 @@
+package com.mycompany.app;
+
+// Exercise 4
+public class Beers
+{
+  public static void main(String... args)
+  {
+    for (int i = 9; i > 1; --i)
+      System.out.printf(
+        "%d bottles of beer we are going to drink, %d bottles of beer.\n"
+        + "Now try to drink one, drink one,\n", i, i);
+    System.out.print(
+      "1 bottle of beer we are going to drink, 1 bottle of beer.\n"
+      + "Now try to drink one, drink one,\n"
+      + "Oh no, no bottles of beer to drink now.\n");
+  }
+}
diff --git a/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/IsLeapYear.java b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/IsLeapYear.java
new file mode 100644
index 0000000..f21b4b3
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/IsLeapYear.java
@@ -0,0 +1,14 @@
+package com.mycompany.app;
+
+// Exercise 7
+public class IsLeapYear
+{
+  public static void main(String... args)
+  {
+    int n = Integer.parseInt(args[0]);
+    if (n % 4 == 0 && n % 100 != 0 || n % 400 == 0)
+      System.out.printf("%d is a leap year\n", n);
+    else
+      System.out.printf("%d is not a leap year\n", n);
+  }
+}
diff --git a/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Linear.java b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Linear.java
new file mode 100644
index 0000000..e7a8413
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Linear.java
@@ -0,0 +1,12 @@
+package com.mycompany.app;
+
+// Exercise 5
+public class Linear
+{
+  public static void main(String... args)
+  {
+    double a = Double.parseDouble(args[0]);
+    double b = Double.parseDouble(args[1]);
+    System.out.println(-b / a);
+  }
+}
diff --git a/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/MeanSTD.java b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/MeanSTD.java
new file mode 100644
index 0000000..eb47914
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/MeanSTD.java
@@ -0,0 +1,17 @@
+package com.mycompany.app;
+
+import java.util.Arrays;
+
+// Exercise 8
+public class MeanSTD
+{
+  public static void main(String... args)
+  {
+    double n = args.length;
+    double m = Arrays.stream(args).mapToDouble(Double::parseDouble).sum() / n;
+    double s = Math.sqrt(
+      Arrays.stream(args)
+      .mapToDouble(x -> Math.pow(Double.parseDouble(x) - m, 2)).sum() / n);
+    System.out.printf("Mean: %f\nStandard deviation: %f\n", m, s);
+  }
+}
diff --git a/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Quadratic.java b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Quadratic.java
new file mode 100644
index 0000000..84d3ecd
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Quadratic.java
@@ -0,0 +1,24 @@
+package com.mycompany.app;
+
+// Exercise 6
+public class Quadratic
+{
+  public static void main(String... args)
+  {
+    double a = Double.parseDouble(args[0]);
+    double b = Double.parseDouble(args[1]);
+    double c = Double.parseDouble(args[2]);
+    // assume ax^2 + bx + c = 0 is a valid quadratic equation
+    double d = b*b - a*c*4;
+    if (d < 0)
+      {
+        System.out.printf("%f + %fj\n", -b/a/2, Math.sqrt(-d)/a/2);
+        System.out.printf("%f + %fj\n", -b/a/2, -Math.sqrt(-d)/a/2);
+      }
+    else
+      {
+        System.out.println(-b/a/2 + Math.sqrt(d)/a/2);
+        System.out.println(-b/a/2 - Math.sqrt(d)/a/2);
+      }
+  }
+}
diff --git a/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/RandRange.java b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/RandRange.java
new file mode 100644
index 0000000..f5c5ffd
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/RandRange.java
@@ -0,0 +1,13 @@
+package com.mycompany.app;
+
+import java.util.concurrent.ThreadLocalRandom;
+
+// Exercise 3
+class RandRange
+{
+  public static void main(String... args)
+  {
+    System.out.println(
+      ThreadLocalRandom.current().nextInt(0, Integer.parseInt(args[0])));
+  }
+}
diff --git a/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/TenHellos.java b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/TenHellos.java
new file mode 100644
index 0000000..a517d39
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/TenHellos.java
@@ -0,0 +1,10 @@
+package com.mycompany.app;
+
+public class TenHellos
+{
+  public static void main(String... args)
+  {
+    for (int i = 0; i < 10; ++i)
+      System.out.println("Hello, World!");
+  }
+}
diff --git a/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/UseThree.java b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/UseThree.java
new file mode 100644
index 0000000..a139fc8
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/UseThree.java
@@ -0,0 +1,11 @@
+package com.mycompany.app;
+
+// Exercise 2
+class UseThree
+{
+  public static void main(String... args)
+  {
+    System.out.printf("Hi %s, %s and %s.  How are you?\n",
+                      args[2], args[1], args[0]);
+  }
+}
diff --git a/usth/ICT2.2/labwork/2/my-app/src/test/java/com/mycompany/app/AppTest.java b/usth/ICT2.2/labwork/2/my-app/src/test/java/com/mycompany/app/AppTest.java
new file mode 100644
index 0000000..4291826
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/src/test/java/com/mycompany/app/AppTest.java
@@ -0,0 +1,16 @@
+package com.mycompany.app;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+// Unit test for simple App.
+public class AppTest 
+{
+  // Rigorous Test :-)
+  @Test
+  public void shouldAnswerWithTrue()
+  {
+    assertTrue( true );
+  }
+}
diff --git a/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/App.class b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/App.class
new file mode 100644
index 0000000..740d561
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/App.class
Binary files differdiff --git a/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/Beers.class b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/Beers.class
new file mode 100644
index 0000000..ff4573d
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/Beers.class
Binary files differdiff --git a/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/IsLeapYear.class b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/IsLeapYear.class
new file mode 100644
index 0000000..f8464c6
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/IsLeapYear.class
Binary files differdiff --git a/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/Linear.class b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/Linear.class
new file mode 100644
index 0000000..6797c5e
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/Linear.class
Binary files differdiff --git a/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/MeanSTD.class b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/MeanSTD.class
new file mode 100644
index 0000000..8da82c5
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/MeanSTD.class
Binary files differdiff --git a/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/Quadratic.class b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/Quadratic.class
new file mode 100644
index 0000000..15b1c7b
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/Quadratic.class
Binary files differdiff --git a/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/RandRange.class b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/RandRange.class
new file mode 100644
index 0000000..9fe4ac3
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/RandRange.class
Binary files differdiff --git a/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/TenHellos.class b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/TenHellos.class
new file mode 100644
index 0000000..ce0b894
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/TenHellos.class
Binary files differdiff --git a/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/UseThree.class b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/UseThree.class
new file mode 100644
index 0000000..b66069e
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/classes/com/mycompany/app/UseThree.class
Binary files differdiff --git a/usth/ICT2.2/labwork/2/my-app/target/maven-archiver/pom.properties b/usth/ICT2.2/labwork/2/my-app/target/maven-archiver/pom.properties
new file mode 100644
index 0000000..248310d
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/maven-archiver/pom.properties
@@ -0,0 +1,4 @@
+#Created by Apache Maven 3.6.2
+groupId=com.mycompany.app
+artifactId=my-app
+version=1.0-SNAPSHOT
diff --git a/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/compile/default-compile/createdFiles.lst b/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/compile/default-compile/createdFiles.lst
new file mode 100644
index 0000000..5a3a47c
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/compile/default-compile/createdFiles.lst
@@ -0,0 +1,9 @@
+com/mycompany/app/App.class
+com/mycompany/app/UseThree.class
+com/mycompany/app/Linear.class
+com/mycompany/app/TenHellos.class
+com/mycompany/app/MeanSTD.class
+com/mycompany/app/RandRange.class
+com/mycompany/app/Beers.class
+com/mycompany/app/IsLeapYear.class
+com/mycompany/app/Quadratic.class
diff --git a/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/compile/default-compile/inputFiles.lst b/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/compile/default-compile/inputFiles.lst
new file mode 100644
index 0000000..7c51ee3
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/compile/default-compile/inputFiles.lst
@@ -0,0 +1,9 @@
+/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Quadratic.java
+/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/IsLeapYear.java
+/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/App.java
+/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/RandRange.java
+/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Beers.java
+/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/Linear.java
+/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/TenHellos.java
+/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/MeanSTD.java
+/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/src/main/java/com/mycompany/app/UseThree.java
diff --git a/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/testCompile/default-testCompile/createdFiles.lst b/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/testCompile/default-testCompile/createdFiles.lst
new file mode 100644
index 0000000..6348184
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/testCompile/default-testCompile/createdFiles.lst
@@ -0,0 +1 @@
+com/mycompany/app/AppTest.class
diff --git a/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/testCompile/default-testCompile/inputFiles.lst b/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/testCompile/default-testCompile/inputFiles.lst
new file mode 100644
index 0000000..543454e
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/maven-status/maven-compiler-plugin/testCompile/default-testCompile/inputFiles.lst
@@ -0,0 +1 @@
+/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/src/test/java/com/mycompany/app/AppTest.java
diff --git a/usth/ICT2.2/labwork/2/my-app/target/my-app-1.0-SNAPSHOT.jar b/usth/ICT2.2/labwork/2/my-app/target/my-app-1.0-SNAPSHOT.jar
new file mode 100644
index 0000000..30b9fdc
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/my-app-1.0-SNAPSHOT.jar
Binary files differdiff --git a/usth/ICT2.2/labwork/2/my-app/target/surefire-reports/TEST-com.mycompany.app.AppTest.xml b/usth/ICT2.2/labwork/2/my-app/target/surefire-reports/TEST-com.mycompany.app.AppTest.xml
new file mode 100644
index 0000000..4041d13
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/surefire-reports/TEST-com.mycompany.app.AppTest.xml
@@ -0,0 +1,60 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<testsuite xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://maven.apache.org/surefire/maven-surefire-plugin/xsd/surefire-test-report.xsd" name="com.mycompany.app.AppTest" time="0.019" tests="1" errors="0" skipped="0" failures="0">
+  <properties>
+    <property name="awt.toolkit" value="sun.awt.X11.XToolkit"/>
+    <property name="java.specification.version" value="11"/>
+    <property name="sun.cpu.isalist" value=""/>
+    <property name="sun.jnu.encoding" value="UTF-8"/>
+    <property name="java.class.path" value="/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/target/test-classes:/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/target/classes:/home/cnx/.m2/repository/junit/junit/4.11/junit-4.11.jar:/home/cnx/.m2/repository/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar:"/>
+    <property name="java.vm.vendor" value="Debian"/>
+    <property name="sun.arch.data.model" value="64"/>
+    <property name="java.vendor.url" value="https://tracker.debian.org/openjdk-11"/>
+    <property name="user.timezone" value=""/>
+    <property name="java.vm.specification.version" value="11"/>
+    <property name="os.name" value="Linux"/>
+    <property name="sun.java.launcher" value="SUN_STANDARD"/>
+    <property name="user.country" value="US"/>
+    <property name="sun.boot.library.path" value="/usr/lib/jvm/java-11-openjdk-amd64/lib"/>
+    <property name="sun.java.command" value="/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/target/surefire/surefirebooter4171187558944627507.jar /home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/target/surefire 2019-10-09T17-47-23_851-jvmRun1 surefire1053437032396327338tmp surefire_014762799941833427558tmp"/>
+    <property name="jdk.debug" value="release"/>
+    <property name="surefire.test.class.path" value="/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/target/test-classes:/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/target/classes:/home/cnx/.m2/repository/junit/junit/4.11/junit-4.11.jar:/home/cnx/.m2/repository/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar:"/>
+    <property name="sun.cpu.endian" value="little"/>
+    <property name="user.home" value="/home/cnx"/>
+    <property name="user.language" value="en"/>
+    <property name="java.specification.vendor" value="Oracle Corporation"/>
+    <property name="java.version.date" value="2019-10-15"/>
+    <property name="java.home" value="/usr/lib/jvm/java-11-openjdk-amd64"/>
+    <property name="file.separator" value="/"/>
+    <property name="basedir" value="/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app"/>
+    <property name="java.vm.compressedOopsMode" value="32-bit"/>
+    <property name="line.separator" value="&#10;"/>
+    <property name="java.specification.name" value="Java Platform API Specification"/>
+    <property name="java.vm.specification.vendor" value="Oracle Corporation"/>
+    <property name="java.awt.graphicsenv" value="sun.awt.X11GraphicsEnvironment"/>
+    <property name="surefire.real.class.path" value="/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app/target/surefire/surefirebooter4171187558944627507.jar"/>
+    <property name="sun.management.compiler" value="HotSpot 64-Bit Tiered Compilers"/>
+    <property name="java.runtime.version" value="11.0.5-ea+6-post-Debian-2"/>
+    <property name="user.name" value="cnx"/>
+    <property name="path.separator" value=":"/>
+    <property name="os.version" value="4.19.0-5-amd64"/>
+    <property name="java.runtime.name" value="OpenJDK Runtime Environment"/>
+    <property name="file.encoding" value="UTF-8"/>
+    <property name="java.vm.name" value="OpenJDK 64-Bit Server VM"/>
+    <property name="localRepository" value="/home/cnx/.m2/repository"/>
+    <property name="java.vendor.url.bug" value="https://bugs.debian.org/openjdk-11"/>
+    <property name="java.io.tmpdir" value="/tmp"/>
+    <property name="java.version" value="11.0.5-ea"/>
+    <property name="user.dir" value="/home/cnx/Documents/B2/ICT2.2/labwork/2/my-app"/>
+    <property name="os.arch" value="amd64"/>
+    <property name="java.vm.specification.name" value="Java Virtual Machine Specification"/>
+    <property name="java.awt.printerjob" value="sun.print.PSPrinterJob"/>
+    <property name="sun.os.patch.level" value="unknown"/>
+    <property name="java.library.path" value="/usr/java/packages/lib:/usr/lib/x86_64-linux-gnu/jni:/lib/x86_64-linux-gnu:/usr/lib/x86_64-linux-gnu:/usr/lib/jni:/lib:/usr/lib"/>
+    <property name="java.vendor" value="Debian"/>
+    <property name="java.vm.info" value="mixed mode, sharing"/>
+    <property name="java.vm.version" value="11.0.5-ea+6-post-Debian-2"/>
+    <property name="sun.io.unicode.encoding" value="UnicodeLittle"/>
+    <property name="java.class.version" value="55.0"/>
+  </properties>
+  <testcase name="shouldAnswerWithTrue" classname="com.mycompany.app.AppTest" time="0.001"/>
+</testsuite>
\ No newline at end of file
diff --git a/usth/ICT2.2/labwork/2/my-app/target/surefire-reports/com.mycompany.app.AppTest.txt b/usth/ICT2.2/labwork/2/my-app/target/surefire-reports/com.mycompany.app.AppTest.txt
new file mode 100644
index 0000000..1c0c529
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/surefire-reports/com.mycompany.app.AppTest.txt
@@ -0,0 +1,4 @@
+-------------------------------------------------------------------------------
+Test set: com.mycompany.app.AppTest
+-------------------------------------------------------------------------------
+Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.019 s - in com.mycompany.app.AppTest
diff --git a/usth/ICT2.2/labwork/2/my-app/target/test-classes/com/mycompany/app/AppTest.class b/usth/ICT2.2/labwork/2/my-app/target/test-classes/com/mycompany/app/AppTest.class
new file mode 100644
index 0000000..88a6c58
--- /dev/null
+++ b/usth/ICT2.2/labwork/2/my-app/target/test-classes/com/mycompany/app/AppTest.class
Binary files differdiff --git a/usth/ICT2.2/labwork/3/3_labwork3.pdf b/usth/ICT2.2/labwork/3/3_labwork3.pdf
new file mode 100644
index 0000000..0c9c533
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/3_labwork3.pdf
Binary files differdiff --git a/usth/ICT2.2/labwork/3/C++/README.md b/usth/ICT2.2/labwork/3/C++/README.md
new file mode 100644
index 0000000..8cd208f
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/README.md
@@ -0,0 +1,10 @@
+# Labwork 3: Implementations in C++
+
+At this point I've come to realized that like Thanos, C++ is inevitable.
+Despite my disgust toward the language (TBH I don't like Java any better),
+I need to know it enough, at least at the read-only level.
+
+Compilation of tests could be done as follows (on Unix-like system of course,
+since poor Windows users don't even have a standard C/C++ compiler):
+
+    c++ <classname>*.cc
diff --git a/usth/ICT2.2/labwork/3/C++/automobile.cc b/usth/ICT2.2/labwork/3/C++/automobile.cc
new file mode 100644
index 0000000..d274a60
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/automobile.cc
@@ -0,0 +1,56 @@
+#include <regex>
+#include <stdexcept>
+#include <string>
+
+#include "automobile.h"
+
+using namespace std;
+
+const regex license_pattern ("[0-9A-Z]+");
+
+void
+Automobile::set_license (string s)
+{
+  smatch m;
+  if (!regex_match (s, m, license_pattern))
+    throw invalid_argument{"invalid license plate"};
+  license = s;
+}
+
+void
+Automobile::set_fuel (double x)
+{
+  if (x < 0)
+    throw invalid_argument{"negative fuel"};
+  fuel = x;
+}
+
+void
+Automobile::set_speed (double x)
+{
+  speed = (x < 0) ? 0 : x;
+}
+
+Automobile::Automobile (string l, double f, double s)
+{
+  set_license (l);
+  set_fuel (f);
+  set_speed (s);
+}
+
+void
+Automobile::accelerate (double v)
+{
+  if (v < 0)
+    throw invalid_argument{"negative acceleration"};
+  if (fuel)
+    set_speed (speed + v);
+}
+
+void
+Automobile::decelerate (double v)
+{
+  if (v < 0)
+    throw invalid_argument{"negative deceleration"};
+  set_speed (speed - v);
+}
diff --git a/usth/ICT2.2/labwork/3/C++/automobile.h b/usth/ICT2.2/labwork/3/C++/automobile.h
new file mode 100644
index 0000000..0e65865
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/automobile.h
@@ -0,0 +1,20 @@
+#include <string>
+
+using namespace std;
+
+class Automobile
+{
+  double fuel;
+  double speed;
+  string license;
+public:
+  Automobile (string, double, double);
+  string get_license () { return license; }
+  double get_fuel () { return fuel; }
+  double get_speed () { return speed; }
+  void set_license (string);
+  void set_fuel (double);
+  void set_speed (double);
+  void accelerate (double);
+  void decelerate (double);
+};
diff --git a/usth/ICT2.2/labwork/3/C++/button-test.cc b/usth/ICT2.2/labwork/3/C++/button-test.cc
new file mode 100644
index 0000000..7164b2f
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/button-test.cc
@@ -0,0 +1,14 @@
+#include <iostream>
+
+#include "button.h"
+
+using namespace std;
+
+int
+main ()
+{
+  Button butt ("foo", "bar");
+  butt.depress ();
+  butt.undepress ();
+  cout << "button " << butt.label << " color " << butt.color << endl;
+}
diff --git a/usth/ICT2.2/labwork/3/C++/button.h b/usth/ICT2.2/labwork/3/C++/button.h
new file mode 100644
index 0000000..92fa685
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/button.h
@@ -0,0 +1,14 @@
+#include <string>
+
+using namespace std;
+
+class Button
+{
+  bool state;
+public:
+  string label;
+  string color;
+  Button (string l, string c) : label {l}, color {c}, state {false} {}
+  void depress () { state = true; }
+  void undepress () { state = false; }
+};
diff --git a/usth/ICT2.2/labwork/3/C++/cow-test.cc b/usth/ICT2.2/labwork/3/C++/cow-test.cc
new file mode 100644
index 0000000..ea7b86d
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/cow-test.cc
@@ -0,0 +1,9 @@
+#include "cow.h"
+
+int
+main ()
+{
+  Cow cow ("foo", "bar", 7);
+  cow.age = -4;   // some casting happens here
+  cow.moo ();
+}
diff --git a/usth/ICT2.2/labwork/3/C++/cow.cc b/usth/ICT2.2/labwork/3/C++/cow.cc
new file mode 100644
index 0000000..84fabc8
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/cow.cc
@@ -0,0 +1,11 @@
+#include <iostream>
+
+#include "cow.h"
+
+using namespace std;
+
+void
+Cow::moo ()
+{
+  cout << "Moo...!" << endl;
+}
diff --git a/usth/ICT2.2/labwork/3/C++/cow.h b/usth/ICT2.2/labwork/3/C++/cow.h
new file mode 100644
index 0000000..df7ffd9
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/cow.h
@@ -0,0 +1,17 @@
+#include <string>
+
+using namespace std;
+
+class Cow
+{
+  // The reason these have private access
+  // is that their no way a cow's name and breed can be changed.
+  string name;
+  string breed;
+public:
+  unsigned age;
+
+  Cow (string n, string b, unsigned a) : name {n}, breed {b}, age {a} {}
+  Cow (string n, string b) : name {n}, breed {b}, age {0} {}
+  void moo ();
+};
diff --git a/usth/ICT2.2/labwork/3/C++/name-card-test.cc b/usth/ICT2.2/labwork/3/C++/name-card-test.cc
new file mode 100644
index 0000000..b459d0d
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/name-card-test.cc
@@ -0,0 +1,14 @@
+#include <iostream>
+
+#include "name-card.h"
+
+using namespace std;
+
+int
+main ()
+{
+  NameCard card ("Foobar Baz", "420-69", "foo@bar.baz");
+  cout << "Name: " << card.get_name () << endl
+       << "Phone: " << card.get_phone () << endl
+       << "Email: " << card.get_email () << endl;
+}
diff --git a/usth/ICT2.2/labwork/3/C++/name-card.cc b/usth/ICT2.2/labwork/3/C++/name-card.cc
new file mode 100644
index 0000000..b6c0751
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/name-card.cc
@@ -0,0 +1,47 @@
+#include <regex>
+#include <stdexcept>
+#include <string>
+
+#include "name-card.h"
+
+using namespace std;
+
+const regex name_pattern ("[ A-Za-z]+");
+const regex phone_pattern ("[-0-9]+");
+// This should be good enough I guess?
+const regex email_pattern ("(\\w+)(\\.|_)?(\\w*)@(\\w+)(\\.(\\w+))+");
+
+void
+NameCard::set_name (string s)
+{
+  // I miss Raku so much
+  smatch m;
+  if (!regex_match (s, m, name_pattern))
+    throw invalid_argument{"invalid name"};
+  name = s;
+}
+
+void
+NameCard::set_phone (string s)
+{
+  smatch m;
+  if (!regex_match (s, m, phone_pattern))
+    throw invalid_argument{"invalid number"};
+  phone = s;
+}
+
+void
+NameCard::set_email (string s)
+{
+  smatch m;
+  if (!regex_match (s, m, email_pattern))
+    throw invalid_argument{"invalid name"};
+  email = s;
+}
+
+NameCard::NameCard (string n, string p, string e)
+{
+  set_name (n);
+  set_phone (p);
+  set_email (e);
+}
diff --git a/usth/ICT2.2/labwork/3/C++/name-card.h b/usth/ICT2.2/labwork/3/C++/name-card.h
new file mode 100644
index 0000000..08e76a7
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/name-card.h
@@ -0,0 +1,18 @@
+#include <string>
+
+using namespace std;
+
+class NameCard
+{
+  string name;
+  string phone;
+  string email;
+public:
+  string get_name () { return name; }
+  string get_phone () { return phone; }
+  string get_email () { return email; }
+  void set_name (string);
+  void set_phone (string);
+  void set_email (string);
+  NameCard (string, string, string);
+};
diff --git a/usth/ICT2.2/labwork/3/C++/shopping-cart-test.cc b/usth/ICT2.2/labwork/3/C++/shopping-cart-test.cc
new file mode 100644
index 0000000..4833e70
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/shopping-cart-test.cc
@@ -0,0 +1,19 @@
+#include <iostream>
+
+#include "shopping-cart.h"
+
+using namespace std;
+
+int
+main ()
+{
+  ShoppingCart cart;
+  cart.add_to_cart ("foo");
+  cart.add_to_cart ("foo");
+  cart.add_to_cart ("bar");
+  cart.remove_from_cart ("baz");
+  cout << cart.count ("foo") << ' '
+       << cart.count ("bar") << ' '
+       << cart.count ("baz") << endl;
+  cart.check_out ();
+}
diff --git a/usth/ICT2.2/labwork/3/C++/shopping-cart.h b/usth/ICT2.2/labwork/3/C++/shopping-cart.h
new file mode 100644
index 0000000..c1450e7
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/shopping-cart.h
@@ -0,0 +1,16 @@
+#include <string>
+#include <unordered_map>
+
+using namespace std;
+
+class ShoppingCart
+{
+  // quite of an improvement over the Java version
+  unordered_map<string, int> contents;
+public:
+  void add_to_cart (string item) { contents[item]++; }
+  void remove_from_cart (string item) { contents[item] = 0; }
+  // to make this class useful anyhow
+  int count (string item) { return contents[item]; }
+  void check_out () { contents.clear (); }
+};
diff --git a/usth/ICT2.2/labwork/3/C++/vector-test.cc b/usth/ICT2.2/labwork/3/C++/vector-test.cc
new file mode 100644
index 0000000..647c8a6
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/vector-test.cc
@@ -0,0 +1,20 @@
+#include <iostream>
+
+#include "vector.h"
+
+using namespace std;
+
+int
+main ()
+{
+  Vector u (4, 20);
+  Vector v (6, 9);
+  cout << "u = (" << u.x << ", " << u.y << ")" << endl;
+  cout << "v = (" << v.x << ", " << v.y << ")" << endl;
+  Vector w {u + v};
+  cout << "u + v = (" << w.x << ", " << w.y << ")" << endl;
+  w = u - v;
+  cout << "u - v = (" << w.x << ", " << w.y << ")" << endl;
+  w = u * v;
+  cout << "u * v = (" << w.x << ", " << w.y << ")" << endl;
+}
diff --git a/usth/ICT2.2/labwork/3/C++/vector.cc b/usth/ICT2.2/labwork/3/C++/vector.cc
new file mode 100644
index 0000000..5ac56de
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/vector.cc
@@ -0,0 +1,19 @@
+#include "vector.h"
+
+Vector
+operator+ (Vector u, Vector v)
+{
+  return u += v;
+}
+
+Vector
+operator- (Vector u, Vector v)
+{
+  return u -= v;
+}
+
+Vector
+operator* (Vector u, Vector v)
+{
+  return u *= v;
+}
diff --git a/usth/ICT2.2/labwork/3/C++/vector.h b/usth/ICT2.2/labwork/3/C++/vector.h
new file mode 100644
index 0000000..8433e79
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/C++/vector.h
@@ -0,0 +1,17 @@
+class Vector
+{
+public:
+  int x;
+  int y;
+
+  Vector (int ex, int why) : x {ex}, y {why} {}
+  Vector () : x {0}, y{0} {}
+
+  Vector& operator+= (Vector v) { x += v.x, y += v.y; return *this; }
+  Vector& operator-= (Vector v) { x -= v.x, y -= v.y; return *this; }
+  Vector& operator*= (Vector v) { x *= v.x, y *= v.y; return *this; }
+};
+
+Vector operator+ (Vector, Vector);
+Vector operator- (Vector, Vector);
+Vector operator* (Vector, Vector);
diff --git a/usth/ICT2.2/labwork/3/Java/Automobile.java b/usth/ICT2.2/labwork/3/Java/Automobile.java
new file mode 100644
index 0000000..14a82ef
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/Automobile.java
@@ -0,0 +1,68 @@
+import java.util.regex.Pattern;
+
+class Automobile
+{
+  private static final Pattern licensePattern = Pattern.compile("[0-9A-Z]+");
+  private double fuel;
+  private double speed;
+  private String license;
+
+  public double getFuel()
+  {
+    return fuel;
+  }
+
+  public double getSpeed()
+  {
+    return speed;
+  }
+
+  public String getLicense()
+  {
+    return license;
+  }
+
+  public void setFuel(double fuel)
+  {
+    if (fuel < 0)
+      throw new IllegalArgumentException(
+        "fuel must be nonnegative, instead got " + fuel);
+    this.fuel = fuel;
+  }
+
+  public void setSpeed(double speed)
+  {
+    this.speed = Math.max(0, speed);
+  }
+
+  public void setLicense(String license)
+  {
+    if (!licensePattern.matcher(license).matches())
+      throw new IllegalArgumentException("invalid license: " + license);
+    this.license = license;
+  }
+
+  public Automobile(double f, double s, String l)
+  {
+    setFuel(f);
+    setSpeed(s);
+    setLicense(l);
+  }
+
+  public void accelerate(double v)
+  {
+    if (v < 0)
+      throw new IllegalArgumentException(
+        "acceleration must be nonnegative, instead got " + v);
+    if (fuel > 0)
+      setSpeed(speed + v);
+  }
+
+  public void decelerate(double v)
+  {
+    if (v < 0)
+      throw new IllegalArgumentException(
+        "deceleration must be nonnegative, instead got " + v);
+    setSpeed(speed - v);
+  }
+}
diff --git a/usth/ICT2.2/labwork/3/Java/Button.java b/usth/ICT2.2/labwork/3/Java/Button.java
new file mode 100644
index 0000000..8a26b3f
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/Button.java
@@ -0,0 +1,50 @@
+public class Button
+{
+  private String label;
+  private String color;
+  private boolean state;
+
+  public Button(String label, String color)
+  {
+    this.label = label;
+    this.color = color;
+    this.state = false;
+  }
+
+  public String toString()
+  {
+    return String.format("<button %s with color %s and state %s>",
+                         label, color, state);
+  }
+
+  // To be honest these getters and setters are really redundant in this case
+  public String getLabel()
+  {
+    return label;
+  }
+
+  public String getColor()
+  {
+    return color;
+  }
+
+  public void setLabel(String label)
+  {
+    this.label = label;
+  }
+
+  public void setColor(String color)
+  {
+    this.color = color;
+  }
+
+  public void dePress()
+  {
+    this.state = true;
+  }
+
+  public void unDepress()
+  {
+    this.state = false;
+  }
+}
diff --git a/usth/ICT2.2/labwork/3/Java/ButtonTest.java b/usth/ICT2.2/labwork/3/Java/ButtonTest.java
new file mode 100644
index 0000000..51dd4d2
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/ButtonTest.java
@@ -0,0 +1,12 @@
+class ButtonTest
+{
+  public static void main(String... args)
+  {
+    Button button = new Button("foo", "bar");
+    System.out.println(button);
+    button.setLabel("fu");
+    button.setColor("baz");
+    button.dePress();
+    System.out.println(button);
+  }
+}
diff --git a/usth/ICT2.2/labwork/3/Java/Cow.java b/usth/ICT2.2/labwork/3/Java/Cow.java
new file mode 100644
index 0000000..36a1051
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/Cow.java
@@ -0,0 +1,36 @@
+public class Cow
+{
+  private String name;
+  private String breed;
+  private int age;
+
+  public Cow(String name, String breed)
+  {
+    this(name, breed, 0);
+  }
+
+  public Cow(String name, String breed, int age)
+  {
+    this.name = name;
+    this.breed = breed;
+    setAge(age);
+  }
+
+  public static void moo()
+  {
+    System.out.println("Moo...!");
+  }
+
+  public int getAge()
+  {
+    return age;
+  }
+
+  public void setAge(int age)
+  {
+    if (age < 0)
+      throw new IllegalArgumentException(
+        "age must be nonnegative, instead got " + age);
+    this.age = age;
+  }
+}
diff --git a/usth/ICT2.2/labwork/3/Java/CowTest.java b/usth/ICT2.2/labwork/3/Java/CowTest.java
new file mode 100644
index 0000000..1a13f67
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/CowTest.java
@@ -0,0 +1,9 @@
+class CowTest   // there's no reason to import a test what-so-ever
+{
+  public static void main(String... args)
+  {
+    Cow cow = new Cow("foo", "bar", 7);
+    cow.setAge(-4);
+    cow.moo();
+  }
+}
diff --git a/usth/ICT2.2/labwork/3/Java/NameCard.java b/usth/ICT2.2/labwork/3/Java/NameCard.java
new file mode 100644
index 0000000..165d5f9
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/NameCard.java
@@ -0,0 +1,67 @@
+import java.util.regex.Pattern;
+
+public class NameCard
+{
+  private static final Pattern namePattern = Pattern.compile("[ A-Za-z]+");
+  private static final Pattern phonePattern = Pattern.compile("[-0-9]*");
+  // I have not learnt regex properly
+  private static final Pattern emailPattern = Pattern.compile(
+    "(\\w+)(\\.|_)?(\\w*)@(\\w+)(\\.(\\w+))+");
+
+  private String name;
+  private String phone;
+  private String email;
+
+  public String getName()
+  {
+    return name;
+  }
+
+  public String getPhone()
+  {
+    return phone;
+  }
+
+  public String getEmail()
+  {
+    return email;
+  }
+
+  public void setName(String name)
+  {
+    if (!namePattern.matcher(name).matches())
+      throw new IllegalArgumentException("invalid name: " + name);
+    this.name = name;
+  }
+
+  public void setPhone(String phone)
+  {
+    if (!phonePattern.matcher(phone).matches())
+      throw new IllegalArgumentException("invalid phone number: " + phone);
+    this.phone = phone;
+  }
+
+  public void setEmail(String email)
+  {
+    if (!emailPattern.matcher(email).matches())
+      throw new IllegalArgumentException("invalid email: " + email);
+    this.email = email;
+  }
+
+  public NameCard(String name)
+  {
+    this(name, "", "");
+  }
+
+  public NameCard(String name, String phone)
+  {
+    this(name, phone, "");
+  }
+
+  public NameCard(String name, String phone, String email)
+  {
+    setName(name);
+    setPhone(phone);
+    setEmail(email);
+  }
+}
diff --git a/usth/ICT2.2/labwork/3/Java/NameCardTest.java b/usth/ICT2.2/labwork/3/Java/NameCardTest.java
new file mode 100644
index 0000000..ed66343
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/NameCardTest.java
@@ -0,0 +1,9 @@
+class NameCardTest
+{
+  public static void main(String... args)
+  {
+    NameCard card = new NameCard("Foobar Baz", "420-69", "foo@bar.baz");
+    System.out.printf("Name: %s\nPhone: %s\nEmail: %s\n",
+                      card.getName(), card.getPhone(), card.getEmail());
+  }
+}
diff --git a/usth/ICT2.2/labwork/3/Java/README.md b/usth/ICT2.2/labwork/3/Java/README.md
new file mode 100644
index 0000000..f0c494a
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/README.md
@@ -0,0 +1,10 @@
+# Labwork 3: Implementations in Java
+
+For the ease of typing, the test files are named `<classname>Test.java`
+instead of `<classname>TestDrive.java`.
+To rename them to the original requirement, use Perl `rename` and GNU `sed`
+
+```sh
+rename s/Test/TestDrive/ *Test.java
+sed -i s/Test/TestDrive/ *TestDrive.java
+```
diff --git a/usth/ICT2.2/labwork/3/Java/ShoppingCart.java b/usth/ICT2.2/labwork/3/Java/ShoppingCart.java
new file mode 100644
index 0000000..f5e23ad
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/ShoppingCart.java
@@ -0,0 +1,27 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class ShoppingCart
+{
+  private List<String> cartContents = new ArrayList<String>();
+
+  public boolean addToCart(String content)
+  {
+    return cartContents.add(content);
+  }
+
+  public boolean removeFromCart(String content)
+  {
+    return cartContents.remove(content);
+  }
+
+  public void checkOut()
+  {
+    cartContents.clear();
+  }
+
+  public String toString()
+  {
+    return "Cart content(s): " + String.join(", ", cartContents);
+  }
+}
diff --git a/usth/ICT2.2/labwork/3/Java/ShoppingCartTest.java b/usth/ICT2.2/labwork/3/Java/ShoppingCartTest.java
new file mode 100644
index 0000000..315f9f4
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/ShoppingCartTest.java
@@ -0,0 +1,16 @@
+class ShoppingCartTest
+{
+  public static void main(String... args)
+  {
+    ShoppingCart cart = new ShoppingCart();
+    System.out.println(cart);
+    cart.addToCart("foo");
+    cart.addToCart("bar");
+    cart.addToCart("baz");
+    System.out.println(cart);
+    cart.removeFromCart("bar");
+    System.out.println(cart);
+    cart.checkOut();
+    System.out.println(cart);
+  }
+}
diff --git a/usth/ICT2.2/labwork/3/Java/Vector.java b/usth/ICT2.2/labwork/3/Java/Vector.java
new file mode 100644
index 0000000..3fc9137
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/Vector.java
@@ -0,0 +1,39 @@
+public class Vector
+{
+  // There's nothing to validate
+  public int x;
+  public int y;
+
+  public Vector()
+  {
+    this(0, 0);
+  }
+
+  public Vector(int x, int y)
+  {
+    this.x = x;
+    this.y = y;
+  }
+
+  public String toString()
+  {
+    // I feel bad writing this
+    return "(" + x + ", " + y + ")";
+  }
+
+  public Vector add(Vector other)
+  {
+    return new Vector(this.x + other.x, this.y + other.y);
+  }
+
+  public Vector subtract(Vector other)
+  {
+    return new Vector(this.x - other.x, this.y - other.y);
+  }
+
+  public Vector multiply(Vector other)
+  {
+    // instruction unclear, applying element-wise multiplication
+    return new Vector(this.x * other.x, this.y * other.y);
+  }
+}
diff --git a/usth/ICT2.2/labwork/3/Java/VectorTest.java b/usth/ICT2.2/labwork/3/Java/VectorTest.java
new file mode 100644
index 0000000..4f0a4a3
--- /dev/null
+++ b/usth/ICT2.2/labwork/3/Java/VectorTest.java
@@ -0,0 +1,10 @@
+class VectorTest
+{
+  public static void main(String... args)
+  {
+    Vector u = new Vector(4, 20);
+    Vector v = new Vector(6, 9);
+    System.out.printf("u = %s\nv = %s\nu + v = %s\nu - v = %s\nu * v = %s\n",
+                      u, v, u.add(v), u.subtract(v), u.multiply(v));
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/4_labwork4.pdf b/usth/ICT2.2/labwork/4/4_labwork4.pdf
new file mode 100644
index 0000000..4a4de56
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/4_labwork4.pdf
Binary files differdiff --git a/usth/ICT2.2/labwork/4/BubbleSort.java b/usth/ICT2.2/labwork/4/BubbleSort.java
new file mode 100644
index 0000000..8557c64
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/BubbleSort.java
@@ -0,0 +1,21 @@
+import java.util.ArrayList;
+import java.util.Scanner;
+
+import static java.util.Collections.swap;
+
+class Stats
+{
+  public static void main(String... args)
+  {
+    var scanner = new Scanner(System.in);
+    int n = scanner.nextInt();
+    var numbers = new ArrayList<Double>();
+    for (int i = 0; i < n; ++i)
+      numbers.add(scanner.nextDouble());
+    for (int m = 0; n > 1; n = m, m = 0)
+      for (int i = 1; i < n; ++i)
+        if (numbers.get(i).compareTo(numbers.get(i - 1)) < 0)
+          swap(numbers, m = i, i - 1);
+    System.out.println(numbers);
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/Centroid.java b/usth/ICT2.2/labwork/4/Centroid.java
new file mode 100644
index 0000000..7862cbb
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/Centroid.java
@@ -0,0 +1,26 @@
+import java.util.Scanner;
+
+class Centriod
+{
+  public static void main(String... args)
+  {
+    var scanner = new Scanner(System.in);
+    double m = 0.0, x = 0.0, y = 0.0;
+
+    while (scanner.hasNextDouble())
+      {
+        double n = scanner.nextDouble();
+        if (!scanner.hasNextDouble())
+          break;
+        double s = scanner.nextDouble();
+        if (!scanner.hasNextDouble())
+          break;
+        double i = scanner.nextDouble();
+
+        m += n;
+        x += n * s;
+        y += n * i;
+      }
+    System.out.println(m + " " + x/m + " " + y/m);
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/Closest.java b/usth/ICT2.2/labwork/4/Closest.java
new file mode 100644
index 0000000..2f1e45d
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/Closest.java
@@ -0,0 +1,45 @@
+import java.util.Scanner;
+
+class Closest
+{
+  private static double x, y, z;
+
+  private static double dist(double a, double b, double c)
+  {
+    double g = x - a;
+    double h = y - b;
+    double i = z - c;
+    return g*g + h*h + i*i;
+  }
+
+  public static void main(String... args)
+  {
+    var scanner = new Scanner(System.in);
+    Double length = null;
+    double a = 0.0, b = 0.0, c = 0.0;
+
+    x = Double.parseDouble(args[0]);
+    y = Double.parseDouble(args[1]);
+    z = Double.parseDouble(args[2]);
+    while (scanner.hasNextDouble())
+      {
+        double d = scanner.nextDouble();
+        if (!scanner.hasNextDouble())
+          break;
+        double e = scanner.nextDouble();
+        if (!scanner.hasNextDouble())
+          break;
+        double f = scanner.nextDouble();
+        double len = dist(d, e, f);
+
+        if (length == null || len < length)
+          {
+            length = len;
+            a = d;
+            b = e;
+            c = f;
+          }
+      }
+    System.out.println(a + " " + b + " " + c);
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/Deal.java b/usth/ICT2.2/labwork/4/Deal.java
new file mode 100644
index 0000000..b2d9ba9
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/Deal.java
@@ -0,0 +1,27 @@
+import static java.util.Collections.shuffle;
+import static java.util.stream.Collectors.toList;
+import static java.util.stream.IntStream.range;
+
+class Deal
+{
+  static final String[] suits = {"clubs", "diamonds", "hearts", "spades"};
+  static final String[] ranks = {"Ace", "Two", "Three", "Four", "Five",
+                                 "Six", "Seven", "Eight", "Nine", "Ten",
+                                 "Jack", "Queen", "King"};
+
+  public static void main(String... args)
+  {
+    var deck = range(0, 52).boxed().collect(toList());
+    shuffle(deck);
+
+    // I have no time handling exceptions.
+    int n = Integer.parseInt(args[0]) % 52;
+    while (n-- > 0)
+      {
+        int card = deck.get(n);
+        int suit = card / 13;
+        int rank = card % 13;
+        System.out.printf("%s of %s\n", ranks[rank], suits[suit]);
+      }
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/DiscreteDistro.java b/usth/ICT2.2/labwork/4/DiscreteDistro.java
new file mode 100644
index 0000000..b603ed7
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/DiscreteDistro.java
@@ -0,0 +1,23 @@
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.stream.Stream;
+
+import static java.util.Collections.binarySearch;
+import static java.util.stream.Collectors.toList;
+
+class DiscreteDistro
+{
+  public static void main(String... args)
+  {
+    var numbers = Stream.of(args).mapToInt(Integer::parseInt)
+                                 .boxed().collect(toList());
+    int n = numbers.size();
+    for (int i = 1; i < n; ++i)
+      numbers.set(i, numbers.get(i) + numbers.get(i - 1));
+
+    int x = ThreadLocalRandom.current().nextInt(0, numbers.get(n - 1));
+    int i = binarySearch(numbers, x) + 1;
+    System.out.println(numbers);
+    System.out.println(x);
+    System.out.println((i < 0) ? -i : i);
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/Employ.java b/usth/ICT2.2/labwork/4/Employ.java
new file mode 100644
index 0000000..924e1d3
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/Employ.java
@@ -0,0 +1,30 @@
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.util.ArrayList;
+import java.util.Scanner;
+
+class Employ
+{
+  private static Employee scan(Scanner s)
+  {
+    int ID = s.nextInt();
+    s.nextLine();
+    return new Employee(ID, s.nextLine(), s.nextLine(),
+                        s.nextDouble(), s.nextDouble());
+  }
+
+  public static void main(String... args) throws FileNotFoundException
+  {
+    var stdin = new Scanner(System.in);
+    var f = new File("employees.txt");
+    var file = new Scanner(f);
+    var employees = new ArrayList<Employee>();
+    int n = stdin.nextInt();
+    for (int i = 0; i < n; ++i)
+      {
+        employees.add(scan(stdin));
+        employees.add(scan(file));
+      }
+    employees.forEach(System.out::println);
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/Employee.class b/usth/ICT2.2/labwork/4/Employee.class
new file mode 100644
index 0000000..3176b0c
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/Employee.class
Binary files differdiff --git a/usth/ICT2.2/labwork/4/Employee.java b/usth/ICT2.2/labwork/4/Employee.java
new file mode 100644
index 0000000..51647b5
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/Employee.java
@@ -0,0 +1,27 @@
+public class Employee
+{
+  private int ID;
+  private String name;
+  private String dep;
+  private double basic;
+  private double extra;
+
+  public Employee(int ID, String name, String dep, double basic, double extra)
+  {
+    this.ID = ID;
+    this.name = name;
+    this.dep = dep;
+    this.basic = basic;
+    this.extra = extra;
+  }
+
+  public int getID() { return ID; }
+  public String getName() { return name; }
+  public String getDep() { return dep; }
+  public double getIncome() { return basic + extra*2.5; }
+
+  public String toString()
+  {
+    return String.format("#%d %s [%s]: %g", ID, name, dep, getIncome());
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/HowMany.java b/usth/ICT2.2/labwork/4/HowMany.java
new file mode 100644
index 0000000..16c07bd
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/HowMany.java
@@ -0,0 +1,7 @@
+class HowMany
+{
+  public static void main(String... args)
+  {
+    System.out.println(args.length);
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/LongestRun.java b/usth/ICT2.2/labwork/4/LongestRun.java
new file mode 100644
index 0000000..74c18c7
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/LongestRun.java
@@ -0,0 +1,30 @@
+import java.util.Scanner;
+
+class LongestRun
+{
+  public static void main(String... args)
+  {
+    var scanner = new Scanner(System.in);
+    Integer number = null;
+    Integer length = null;
+    Integer n = null, len = null;
+
+    while (scanner.hasNextInt())
+      {
+        Integer i = scanner.nextInt();
+        if (i == n)
+          {
+            len++;
+            continue;
+          }
+        if (length == null || len > length)
+          {
+            number = n;
+            length = len;
+          }
+        n = i;
+        len = 1;
+      }
+    System.out.printf("Longest run: %d consecutive %d\n", number, length);
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/MaxMin.java b/usth/ICT2.2/labwork/4/MaxMin.java
new file mode 100644
index 0000000..d34c01f
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/MaxMin.java
@@ -0,0 +1,18 @@
+import java.util.ArrayList;
+import java.util.Scanner;
+
+import static java.util.Collections.min;
+import static java.util.Collections.max;
+import static java.util.stream.Collectors.toList;
+
+class MaxMin
+{
+  public static void main(String... args)
+  {
+    var numbers = new ArrayList<Integer>();
+    var scanner = new Scanner(System.in);
+    while (scanner.hasNextInt())
+      numbers.add(scanner.nextInt());
+    System.out.printf("Min: %d\nMax: %d\n", min(numbers), max(numbers));
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/Stats.java b/usth/ICT2.2/labwork/4/Stats.java
new file mode 100644
index 0000000..88d6832
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/Stats.java
@@ -0,0 +1,19 @@
+import java.util.ArrayList;
+import java.util.Scanner;
+
+class Stats
+{
+  public static void main(String... args)
+  {
+    var scanner = new Scanner(System.in);
+    int n = scanner.nextInt();
+    var numbers = new ArrayList<Double>();
+    for (int i = 0; i < n; ++i)
+      numbers.add(scanner.nextDouble());
+
+    double m = numbers.stream().mapToDouble(Double::doubleValue).sum() / n;
+    double s = Math.sqrt(numbers.stream()
+                         .mapToDouble(x -> Math.pow(x - m, 2)).sum() / n);
+    System.out.printf("Mean: %f\nStandard deviation: %f\n", m, s);
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/Transpose.java b/usth/ICT2.2/labwork/4/Transpose.java
new file mode 100644
index 0000000..597a783
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/Transpose.java
@@ -0,0 +1,24 @@
+class Transpose
+{
+  public static void main(String... args)
+  {
+    int[][] m = {{7, 8, 9},
+                 {4, 5, 6},
+                 {1, 2, 3}};
+    int n = 3;  // some sort of abstraction
+    System.out.println("Original matrix:");
+    for (int i = 0; i < n; ++i)
+      System.out.printf("%d %d %d\n", m[i][0], m[i][1], m[i][2]);
+
+    for (int i = 1; i < n; ++i)
+      for (int j = 0; j < i; ++j)
+        {
+          m[i][j] ^= m[j][i];
+          m[j][i] ^= m[i][j];
+          m[i][j] ^= m[j][i];
+        }
+    System.out.println("Transposed matrix:");
+    for (int i = 0; i < n; ++i)
+      System.out.printf("%d %d %d\n", m[i][0], m[i][1], m[i][2]);
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/WordCount.java b/usth/ICT2.2/labwork/4/WordCount.java
new file mode 100644
index 0000000..4d0bfc6
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/WordCount.java
@@ -0,0 +1,16 @@
+import java.util.Scanner;
+
+class WordCount
+{
+  public static void main(String... args)
+  {
+    var scanner = new Scanner(System.in);
+    int count = 0;
+    while (scanner.hasNext())
+      {
+        scanner.next();
+        count++;
+      }
+    System.out.println(count);
+  }
+}
diff --git a/usth/ICT2.2/labwork/4/employees.txt b/usth/ICT2.2/labwork/4/employees.txt
new file mode 100644
index 0000000..7dc4e8f
--- /dev/null
+++ b/usth/ICT2.2/labwork/4/employees.txt
@@ -0,0 +1,8 @@
+7
+Foo Bar
+lmao
+420 69
+3
+Baz Bac
+lol
+1 4
diff --git a/usth/ICT2.2/labwork/5/Java/abstract/Circle.java b/usth/ICT2.2/labwork/5/Java/abstract/Circle.java
new file mode 100644
index 0000000..3ee8c84
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/Java/abstract/Circle.java
@@ -0,0 +1,13 @@
+public class Circle extends Point
+{
+  public double r;
+
+  public Circle(double x, double y, double r)
+  {
+    super(x, y);
+    this.r = r;
+  }
+
+  public double calArea() { return r * r * Math.PI; }
+  public String getName() { return "Circle"; }
+}
diff --git a/usth/ICT2.2/labwork/5/Java/abstract/Cylinder.java b/usth/ICT2.2/labwork/5/Java/abstract/Cylinder.java
new file mode 100644
index 0000000..8fa9e0c
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/Java/abstract/Cylinder.java
@@ -0,0 +1,14 @@
+public class Cylinder extends Circle
+{
+  public double h;
+
+  public Cylinder(double x, double y, double r, double h)
+  {
+    super(x, y, r);
+    this.h = h;
+  }
+
+  public double calArea() { return super.calArea()*2.0 + r*h*Math.PI*2.0; }
+  public double calVolume() { return super.calArea() * h; }
+  public String getName() { return "Circle"; }
+}
diff --git a/usth/ICT2.2/labwork/5/Java/abstract/Point.java b/usth/ICT2.2/labwork/5/Java/abstract/Point.java
new file mode 100644
index 0000000..f6daf22
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/Java/abstract/Point.java
@@ -0,0 +1,13 @@
+public class Point extends Shape
+{
+  public double x;
+  public double y;
+
+  public Point(double x, double y)
+  {
+    this.x = x;
+    this.y = y;
+  }
+
+  public String getName() { return "Point"; }
+}
diff --git a/usth/ICT2.2/labwork/5/Java/abstract/Shape.java b/usth/ICT2.2/labwork/5/Java/abstract/Shape.java
new file mode 100644
index 0000000..dd4124c
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/Java/abstract/Shape.java
@@ -0,0 +1,12 @@
+public abstract class Shape
+{
+  public double calArea() { return 0.0; }
+  public double calVolume() { return 0.0; }
+  public abstract String getName();
+
+  public String toString()
+  {
+    return String.format("%s of area %g and volume %g",
+                         getName(), calArea(), calVolume());
+  }
+}
diff --git a/usth/ICT2.2/labwork/5/Java/abstract/Test.java b/usth/ICT2.2/labwork/5/Java/abstract/Test.java
new file mode 100644
index 0000000..b0502f0
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/Java/abstract/Test.java
@@ -0,0 +1,11 @@
+import static java.util.Arrays.asList;
+
+class Test
+{
+  public static void main(String... args)
+  {
+    var array = asList(new Point(1.0, 2.0), new Circle(3.0, 4.0, 5.0),
+                       new Cylinder(6.0, 7.0, 8.0, 9.0));
+    array.forEach(System.out::println);
+  }
+}
diff --git a/usth/ICT2.2/labwork/5/Java/interface/Circle.java b/usth/ICT2.2/labwork/5/Java/interface/Circle.java
new file mode 100644
index 0000000..3ee8c84
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/Java/interface/Circle.java
@@ -0,0 +1,13 @@
+public class Circle extends Point
+{
+  public double r;
+
+  public Circle(double x, double y, double r)
+  {
+    super(x, y);
+    this.r = r;
+  }
+
+  public double calArea() { return r * r * Math.PI; }
+  public String getName() { return "Circle"; }
+}
diff --git a/usth/ICT2.2/labwork/5/Java/interface/Cylinder.java b/usth/ICT2.2/labwork/5/Java/interface/Cylinder.java
new file mode 100644
index 0000000..8fa9e0c
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/Java/interface/Cylinder.java
@@ -0,0 +1,14 @@
+public class Cylinder extends Circle
+{
+  public double h;
+
+  public Cylinder(double x, double y, double r, double h)
+  {
+    super(x, y, r);
+    this.h = h;
+  }
+
+  public double calArea() { return super.calArea()*2.0 + r*h*Math.PI*2.0; }
+  public double calVolume() { return super.calArea() * h; }
+  public String getName() { return "Circle"; }
+}
diff --git a/usth/ICT2.2/labwork/5/Java/interface/Point.java b/usth/ICT2.2/labwork/5/Java/interface/Point.java
new file mode 100644
index 0000000..90b2569
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/Java/interface/Point.java
@@ -0,0 +1,21 @@
+public class Point implements Shape
+{
+  public double x;
+  public double y;
+
+  public Point(double x, double y)
+  {
+    this.x = x;
+    this.y = y;
+  }
+
+  public double calArea() { return 0.0; }
+  public double calVolume() { return 0.0; }
+  public String getName() { return "Point"; }
+
+  public String toString()
+  {
+    return String.format("%s of area %g and volume %g",
+                         getName(), calArea(), calVolume());
+  }
+}
diff --git a/usth/ICT2.2/labwork/5/Java/interface/Shape.java b/usth/ICT2.2/labwork/5/Java/interface/Shape.java
new file mode 100644
index 0000000..1eb33fa
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/Java/interface/Shape.java
@@ -0,0 +1,6 @@
+interface Shape
+{
+  public double calArea();
+  public double calVolume();
+  public String getName();
+}
diff --git a/usth/ICT2.2/labwork/5/Java/interface/Test.java b/usth/ICT2.2/labwork/5/Java/interface/Test.java
new file mode 100644
index 0000000..b0502f0
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/Java/interface/Test.java
@@ -0,0 +1,11 @@
+import static java.util.Arrays.asList;
+
+class Test
+{
+  public static void main(String... args)
+  {
+    var array = asList(new Point(1.0, 2.0), new Circle(3.0, 4.0, 5.0),
+                       new Cylinder(6.0, 7.0, 8.0, 9.0));
+    array.forEach(System.out::println);
+  }
+}
diff --git a/usth/ICT2.2/labwork/5/virtual.cc b/usth/ICT2.2/labwork/5/virtual.cc
new file mode 100644
index 0000000..23ae78a
--- /dev/null
+++ b/usth/ICT2.2/labwork/5/virtual.cc
@@ -0,0 +1,61 @@
+#include <cmath>
+#include <iostream>
+#include <memory>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+static constexpr double PI = acos (-1.0);
+
+class Shape
+{
+public:
+  virtual string get_name () const = 0;
+
+  virtual double cal_area () const { return 0.0; }
+  virtual double cal_vol () const { return 0.0; }
+};
+
+class Point : public Shape
+{
+public:
+  double x, y;
+  Point (double a, double b) : x {a}, y {b} {}
+
+  string get_name () const override { return "Point"; }
+};
+
+class Circle : public Shape
+{
+public:
+  double x, y, r;
+  Circle (double a, double b, double c) : x {a}, y {b}, r {c} {}
+
+  string get_name () const override { return "Circle"; }
+  double cal_area () const override { return r * r * PI; }
+};
+
+class Cylinder : public Shape
+{
+public:
+  double x, y, r, h;
+  Cylinder (double a, double b, double c, double d)
+    : x {a}, y {b}, r {c}, h {d} {}
+
+  string get_name () const override { return "Cylinder"; }
+  double cal_area () const override { return (r + h) * r * PI * 2.0; }
+  double cal_vol () const override { return r * r * h * PI; }
+};
+
+int
+main ()
+{
+  vector<unique_ptr<Shape>> v;
+  v.push_back (make_unique<Point> (1.0, 2.0));
+  v.push_back (make_unique<Circle> (3.0, 4.0, 5.0));
+  v.push_back (make_unique<Cylinder> (6.0, 7.0, 8.0, 9.0));
+  for (auto& p : v)
+    cout << p->get_name () << " of area " << p->cal_area ()
+         << " and volume " << p->cal_vol () << endl;
+}
diff --git a/usth/ICT2.2/midterm/report/bubbleplot.jpg b/usth/ICT2.2/midterm/report/bubbleplot.jpg
new file mode 100644
index 0000000..13ea13d
--- /dev/null
+++ b/usth/ICT2.2/midterm/report/bubbleplot.jpg
Binary files differdiff --git a/usth/ICT2.2/midterm/report/report.pdf b/usth/ICT2.2/midterm/report/report.pdf
new file mode 100644
index 0000000..4b4ad3c
--- /dev/null
+++ b/usth/ICT2.2/midterm/report/report.pdf
Binary files differdiff --git a/usth/ICT2.2/midterm/report/report.tex b/usth/ICT2.2/midterm/report/report.tex
new file mode 100644
index 0000000..627530a
--- /dev/null
+++ b/usth/ICT2.2/midterm/report/report.tex
@@ -0,0 +1,928 @@
+\documentclass[a4paper,12pt]{article}
+\usepackage[english,vietnamese]{babel}
+\usepackage{amsmath}
+\usepackage{amssymb}
+\usepackage{booktabs}
+\usepackage{lmodern}
+\usepackage{graphicx}
+\usepackage{hyperref}
+\usepackage{lmodern}
+\usepackage{forest}
+\usepackage{textcomp}
+\usepackage[nottoc,numbib]{tocbibind}
+
+\renewcommand{\thefootnote}{\fnsymbol{footnote}}
+
+\begin{document}
+\setcounter{page}{0}
+\thispagestyle{empty}
+\vspace*{\stretch{1}}
+\begin{flushright}
+  \setlength{\baselineskip}{1.4\baselineskip}
+\textbf{\Huge Midterm Report\\Sorting and Searching}
+  \noindent\rule{\textwidth}{5pt}
+  \emph{\Large Object Oriented Programming}
+  \vspace{\stretch{1}}
+
+  \textbf{by Nguyễn Công Thành, Nguyễn Gia Phong\\
+          Nguyễn Văn Tùng, Trần Minh Vương and Trần Hồng Minh\\}
+  \selectlanguage{english}
+  \today
+\end{flushright}
+\vspace*{\stretch{2}}
+\pagebreak
+
+\selectlanguage{english}
+\tableofcontents
+\pagebreak
+
+\section{Introduction}
+\subsection{Brief Description}
+Since the dawn of computer science, sorting and searching algorithms
+have drawn a significant amount of attention from researchers,
+due to their broad applications in solving a huge number of problems
+and sub-problems in many fields.  In spite of their straightforward, familiar
+statements, these algorithm link with a variety of important programming
+concepts, namely data structures, divide and conquer technique and of course
+complexity analysis and time–space tradeoffs.
+
+In this report, we only discuss some of the most basic searching
+and sorting algorithms.  While trying to implement them, we also analyze
+their strengths and weaknesses, as well as the ease and difficulties
+we encounter using the language Java and object-oriented programming in general.
+
+Whilst overall, we follow~\cite{wu}, we also try to make use of newer Java
+features to write more generic and concise code.
+
+This report is licensed under a
+\href{http://creativecommons.org/licenses/by-sa/4.0/}{Creative Commons
+Attribution-ShareAlike 4.0 International License.}
+
+\selectlanguage{vietnamese}
+\subsection{Authors and Credits}
+
+The work has been undertaken by group number 11, whose members are listed
+in the following table, with Nguyễn Công Thành being our leader.
+\begin{center}
+  \begin{tabular}{c c}
+    \toprule
+    Full name & Student ID\\
+    \midrule
+    Nguyễn Công Thành & BI9-210\\
+    Nguyễn Gia Phong & BI9-184\\
+    Nguyễn Văn Tùng & BI9-229\\
+    Trần Minh Vương & BI9-239\\
+    Trần Hồng Minh & BI8-114\\
+    \bottomrule
+  \end{tabular}
+\end{center}
+
+We would like to express our special thanks to Dr. Nghiêm Thị Phương,
+whose lectures gave us basic understanding on the key principles of
+object-oriented programming.  Without her guidance, we might never
+have a chance to take an in-depth exploration on this topic.
+\pagebreak
+
+\selectlanguage{english}
+\section{Searching}
+For the sake of simplicity, we only consider searching operating on array-like
+data structures with constant-time random access and without duplicated entries.
+This affects a few implementation design decision we will be making later on.
+The searching problem is then stated in ~\cite[p.~634]{wu} accordingly:
+\begin{quote}
+  Given a value $x$, return the [zero-based] index of $x$ in the array,
+  if such $x$ exists.  Otherwise, return \verb|NOT_FOUND| (-1).
+\end{quote}
+
+In this section, we will discover two searching algorithms: linear search
+and binary search.  Both of these, albeit being simple, are being used in
+many different programming tasks.
+
+\subsection{Linear Search}
+Linear search, by definition, sequentially checks each element of a list
+until a match is found or the whole list has been searched.  This matches
+the algorithm implemented in \verb|java.util.List.indexOf|~\cite[indexOf]{list}.
+Given
+\begin{verbatim}
+var list = java.util.Arrays.asList(4, 20, 6, 9);
+\end{verbatim}
+where \verb|var| is a Java SE 10 feature for eliding ``the often-unnecessary
+manifest declaration of local variable types''~\cite{var}, which, in this case,
+is \verb|List<Integer>|.
+
+\verb|list.indexOf(6)| would then give 2 and \verb|list.indexOf(7)| returns -1.
+
+For the matter of completeness, we also try to implement the description
+provided by the documentation~\cite[indexOf]{list}
+\begin{verbatim}
+import java.util.List;
+
+public class Search
+{
+  public static final int NOT_FOUND = -1;
+
+  public static linear(List l, Object o)
+  {
+    for (int i = 0; i < l.size(); ++i)
+      if (o == null ? l.get(i) == null : o.equals(l.get(i)))
+        return i;
+    return NOT_FOUND;
+  }
+}
+\end{verbatim}
+
+From this dummy implementation, it is trivial that linear search has,
+as it name suggests, \emph{linear time} complexity.  The nullity check
+every iteration adds a bit of overhead, but if performance is ever concerned,
+the better tested and optimized standard library should be used instead.
+Moving \verb|o == null| to the upper level would require duplicating
+the \verb|for| loop, creating redundancy and making the code less readable
+and less maintainable.
+
+Unsurprisingly, 2 and -1 are returned from
+\verb|Search.linear(list, 6)| and \verb|Search.linear(list, 7)|,
+respectively.
+
+\subsection{Binary Search}
+Binary search find the position of a target value within a sorted array by
+``testing the middle of an interval, eliminating the half of the [array] in
+which the key cannot lie, and then repeating the procedure iteratively''
+\cite{bsearch}.  This could be intuitively implemented using recursion:
+\begin{verbatim}
+// ...
+public class Search
+{
+  // ...
+  private static <T>
+  int binary(List<? extends Comparable<? super T>> list, T key,
+             int low, int high)
+  {
+    if (high < low)
+      return NOT_FOUND;
+    var mid = (low + high) / 2;
+    var cmp = list.get(mid).compareTo(key);
+    if (cmp < 0)
+      return binary(list, key, mid + 1, high);
+    if (cmp > 0)
+      return binary(list, key, low, mid - 1);
+    return mid;
+  }
+}
+\end{verbatim}
+
+\verb|Search.binary| is declared as a \emph{generic method} to allow
+more implicit calls, where the compiler will \emph{infer} the type of \verb|key|
+as well as that of each element of \verb|list|~\cite{infer}.  This makes
+the method work on any type of argument that is a subclass of \verb|Comparable|,
+which is required for \verb|Comparable.compareTo|.  In fact,
+\verb|java.util.Collections.binarySearch|'s declaration follows
+the same strategy~\cite[binarySearch]{collections}.
+
+Instead of directly exposing this method where users need to provide
+the lower and higher bound of the indices, we overload it with a wrapper
+to ensure encapsulation:
+\begin{verbatim}
+// ...
+public class Search
+{
+  // ...
+  public static <T>
+  int binary(List<? extends Comparable<? super T>> list, T key)
+  {
+    return binary(list, key, 0, list.size());
+  }
+}
+\end{verbatim}
+
+To test our implementation, we first need \verb|list| to be sorted.
+By providing \verb|null| to its \verb|sort| method, we can sort it
+in the elements' natural (ascending) order~\cite[sort]{list}.
+As \verb|list| is now [4, 6, 9, 20], \verb|Search.binary(list, 6)|
+and \verb|Search.binary(list, 7)| return 1 and -1 respectively.
+
+\verb|java.util.Collections.binarySearch(list, 7)| gives -3, however,
+due to its slightly different behavior:
+\begin{quote}
+  [If \verb|key| is not in the list, returns] \verb|(-(insertion point) - 1)|.
+  The insertion point is defined as the point at which the key would be
+  inserted into the list: the index of the first element greater than the key,
+  or \verb|list.size()| if all elements in the list are less than
+  the specified key.~\cite[binarySearch]{collections}
+\end{quote}
+
+Since the algorithm only give up the search until the array is bisected to
+a nonpositive length (\verb|high < low|), the time-complexity of binary search
+is asymptotic to $\log_2 n$, where $n$ is the size of the array.
+In other words, on modern 64-bit computers with support for at most 18EB
+of address space, the running time is still negligible (64 comparisons).
+Despite the use of \verb|List| interface in the implementation,
+\verb|Search.binary| is not $\Theta(\lg n)$\footnote{The notation
+$f = \Theta(g)$ indicates that $f$ grows at the same rate as $g$.}
+on \verb|LinkedList|, which has $\Theta(n)$ random access.
+
+Since the algorithm only works on ordered lists, it is not
+suitable for iteratively inserting to a sorted list, as for linear
+data structures, either random access or middle insertion has to be
+$\Omega(n)$\footnote{The notation $f = \Omega(g)$ indicates that $f$ grows at
+least as as fast as $g$.}.  In that case, self-balancing binary search tree
+should be used instead.
+\pagebreak
+
+\section{Sorting}
+The sorting problem is stated in~\cite[p. 638]{wu} as
+\begin{quote}
+  Given an array of $n$ values, arrange the values into ascending order.
+\end{quote}
+
+This section discusses only three sorting algorithms,
+namely selection sort, bubble sort and heapsort.
+
+\subsection{Selection Sort}
+Selection sort could be performed by iterating through every position and select
+the minimum element from the current one to the end of the array.  The in-place
+algorithm could be implemented in Java as follows:
+\begin{verbatim}
+import java.util.List;
+
+import static java.util.Collections.swap;
+
+public class Sort
+{
+  public static <T extends Comparable<? super T>>
+  void selection(List<T> list)
+  {
+    int i, j, m, n = list.size();
+    for (i = 0; i < n; ++i)
+      {
+        for (m = j = i; j < n; ++j)
+          if (list.get(j).compareTo(list.get(m)) < 0)
+            m = j;
+        swap(list, i, m);
+      }
+  }
+}
+\end{verbatim}
+
+Since only atomic \verb|int|'s are introduced, the space complexity is
+$\Theta(1)$.  The time complexity is, in term of swaps, $\Theta(n)$
+and, in term of comparisons,
+\[T(n) = \sum_{i=0}^{n-1}\sum_{j=i}^{n-1}1
+       = \sum_{i=0}^{n-1}(n - i)
+       = \sum_{i=1}^{n}i
+       = \frac{n^2 + n}{2}
+       = \Theta(n^2)\]
+
+One could micro-optimize by tweaking \verb|i|'s and \verb|j|'s
+bounds by an unit but that does not make the algorithm
+any faster asymptotically.
+
+Just to make sure everything works correctly, we do a simple check
+\begin{verbatim}
+var list = java.util.Arrays.asList("foo", "bar", "baz");
+Sort.selection(list);
+System.out.println(list);
+\end{verbatim}
+and get \verb|[bar, baz, foo]| printed to \verb|stdout| as expected.
+
+\subsection{Bubble Sort}
+In~\cite[p. 646]{wu}, the author praised bubble sort to finish sooner than
+selection sort on average and best cases.  Whilst the latter is true,
+we will try to explain why the former is generally incorrect.
+
+To do this, we first need to understand what bubble sort is.
+As defined in~\cite[p. 40]{clrs}, the code below operating on
+an array \verb|a| of size \verb|n| qualifies as bubble sort.
+\begin{verbatim}
+for (int i = n - 1; i > 0; --i)
+  for (int j = 1; j < i; ++j)
+    if (a[j] < a[j - 1])
+      swap(a, j, j - 1);
+\end{verbatim}
+
+This naïve version, like selection sort, has the time complexity $\Theta(n^2)$
+in term of comparisons (it underperform selection sort in term of swaps
+however--this will be discussed right after the implementation is completed).
+Though, as pointed out in~\cite{bubblebad},
+\begin{quote}
+  Nearly every description of bubble sort describes
+  how to terminate the sort early if the vector becomes sorted.
+\end{quote}
+
+Hence, we \emph{upgrade} the pseudocode to
+\begin{verbatim}
+boolean swapped;
+do
+  {
+    swapped = false;
+    for (int j = 1; j < n; ++j)
+      if (a[j] < a[j - 1])
+        {
+          swap(a, j, j - 1);
+          swapped = true;
+        }
+  }
+while (swapped);
+\end{verbatim}
+
+We can do further optimization avoiding comparing the last $t - 1$ items
+when running for the $t$-th time of the outer loop, as after iteration $t - 1$,
+these have already \emph{bubbled up} to its final place~\cite{wikibubble}.
+With this in mind, we write our final implementation:
+\begin{verbatim}
+// ...
+public class Sort
+{
+  // ...
+  public static <T extends Comparable<? super T>>
+  void bubble(List<T> list)
+  {
+    for (int n = list.size(), m = 0; n > 1; n = m, m = 0)
+      for (int i = 1; i < n; ++i)
+        if (list.get(i).compareTo(list.get(i - 1)) < 0)
+          swap(list, m = i, i - 1);
+  }
+}
+\end{verbatim}
+
+In the best case where the list is already sorted, during the first iteration
+of the outer loop, \verb|m| remains zero, which is then assigned to \verb|n|
+to break the loop, hence the time complexity is that of the inner loop
+or $n - 1 = \Omega(n)$.  Otherwise, denote $S$ as a subset of all
+positive integers not greater than \verb|list.size()|.  The time complexity
+would then be
+\[T(n) = \sum_{n\in S}\Theta(n)\]
+On random data, $\#S = \Theta(n)$ and thus $T(n) = \Theta(n^2)$.
+
+As demonstrated in~\cite{bubblebad}, selection sort outperforms bubble sort
+on average cage, despite their asymptotically equivalent time complexity:
+\begin{center}
+  \includegraphics[width=0.57\textwidth]{bubbleplot.jpg}
+\end{center}
+
+Looking back at~\cite[p. 646]{wu}, we are now able to spot Wu's misconception:
+\begin{quote}
+  On average, we expect the bubble sort to finish sorting sooner than
+  the selection sort, \emph{because there will be more data movements for
+  the same number of comparisons}, and there is a test to exit the method
+  when the array gets sorted.
+\end{quote}
+
+While bubble sort may take advantage of the pre-sorted parts of the array
+to do fewer comparisons, the number of swaps is $\Theta(n^2)$, which grows
+strictly faster than selection sort's $\Theta(n)$.  Consequently, instead of
+swapping more to finish faster, the bubble variant does more unnecessary
+data movements.  Furthermore, write operations on memory are usually slower
+than reading, which makes swaps much costlier than comparisons.  Finally,
+it could be summarized by a quote from Donald Knuth~\cite{peculiar},
+\begin{quote}
+  In fact, one of Demuth's main results was that in a certain sense
+  `bubble sorting' is the optimum way to sort.  [...]  It turns out that
+  [all other sorting methods studied] are always better in practice,
+  in spite of the fact that Demuth has proved the optimality of bubble sorting
+  on a certain peculiar type of machine. 
+\end{quote}
+
+\subsection{Heapsort}
+Heapsort could be viewed as an improved version of selection sort, where
+the selection is done on the right data structure: the heap~\cite{heapselect}.
+To sort an array ascendingly in place, we use a binary max-heap to keep track
+of the largest element in the unsorted region and move it to the beginning
+of the sorted one, iteratively.
+
+The binary heap is an array object $A$ which resembles a nearly completely
+filled binary tree, except possibly the lowest level.  This kind of heap has
+two attributes: $length$ of the array and $size$ of the heap,
+where $0 \le size \le length$ and valid elements of the heap only reside
+within the $[0, size)$ index interval of the array~\cite[p. 151]{clrs}.
+
+We choose \verb|java.util.List| as the interface for the inner representation
+of heap and come up with the following declaration:
+\begin{verbatim}
+import java.util.List;
+
+public class Heap<T extends Comparable<? super T>>
+{
+  private List<T> list;
+  private int size;
+  public int getSize()
+  {
+    return size;
+  }
+
+  public int getLength()
+  {
+    return list.size();
+  }
+
+  public T get(int i)
+  {
+    return list.get(i);
+  }
+}
+\end{verbatim}
+
+Since the elements are of the type \verb|Comparable|, \verb|Heap| is a max-heap
+in a purely conceptual sense.  That is, the order totally depends on
+\verb|T.compareTo|, which could be defined or overridden by the users.
+The max-heap property is then defined as that for every node $i$ other than
+the root $A_0$, $A_{\mathrm{parent}(i)} \ge A_i$, where the indices of a node's
+parent, left child and right child are given by
+\[\begin{array}{ll}
+  \mathrm{parent}(i) &= \left\lfloor\dfrac{i - 1}{2}\right\rfloor\\
+  \mathrm{left}(i) &= 2i + 1\\
+  \mathrm{right}(i) &= 2i + 2
+\end{array}\]
+
+To maintain this property at node $i$, with the assumption that
+the binary trees rooted at left($i$) and right($i$) are already max-heaps,
+we use \verb|heapify|, which sift the value at $A_i$ down the heap if it is
+smaller than its children:
+\begin{verbatim}
+// ...
+import static java.util.Collections.swap;
+
+public class Heap<T extends Comparable<? super T>>
+{
+  // ...
+  public void heapify(int i)
+  {
+    int right = i + 1 << 1;
+    int left = right - 1;
+    int largest = i;
+    if (left < size && get(left).compareTo(get(largest)) > 0)
+      largest = left;
+    if (right < size && get(right).compareTo(get(largest)) > 0)
+      largest = right;
+    if (largest != i)
+      {
+        swap(list, i, largest);
+        heapify(largest);
+      }
+  }
+}
+\end{verbatim}
+
+At each call, the index of the greatest element among $A_i$,
+$A_{\mathrm{left}(i)}$ and $A_{\mathrm{right}(i)}$ is assigned
+to \verb|largest|.  In case $A_i$ is greatest, the subtree rooted at $A_i$
+is already a max-heap and the method terminates.  Otherwise, $A_i$ is swapped
+with $A_{\mathtt{largest}}$, which makes node $i$ and its children to satisfy
+the max-heap property.  The subtree rooted at \verb|largest|, though,
+\emph{might} violate the property so \verb|heapify| needs to be called on it.
+For instance, given $i$ points to the subtree on the left, then \verb|heapify|
+would step-by-step turn it to the one on the right:
+\begin{center}
+  \begin{forest}
+    for tree={circle,draw}
+    [,phantom [4,fill=yellow [9 [0] [6]] [8 [3] [,phantom]]]
+              [9 [4,fill=yellow [0] [6]] [8 [3] [,phantom]]]
+              [9 [6 [0] [4,fill=yellow]] [8 [3] [,phantom]]]]
+  \end{forest}
+\end{center}
+
+The running time of \verb|heapify| on a subtree of height (number of edges
+between the root and the furthest leaf) $h$ is the time $\Theta(1)$) to make
+$A_i$, $A_{\mathrm{left}(i)}$ and $A_{\mathrm{right}(i)}$ a max-heap, plus
+the time to run \verb|heapify| on one of its children if necessary:
+\[T(h) \le T(h - 1) + \Theta(1)
+       \le T(0) + \sum_{i=1}^{h}\Theta(1) = T(0) + \Theta(h)\]
+Since $T(0)$ is obviously $\Theta(1)$,
+\[T(h) \leq \Theta(h) \Longrightarrow T(h) = O(h)\footnotemark\]
+A binary tree of size $n$ may have at maximum height of
+$h = \lfloor\log_2 n\rfloor$, thus the time complexity with respect to
+the size of the subtree is $O(\log_2 n)$.
+\footnotetext{The notation $f = O(g)$ indicates that $f$ grows
+at most as as fast as $g$.}
+
+Noticeably, $\forall i \ge \lfloor n/2\rfloor,\; 2i + 2 > 2i + 1 \ge n
+\iff \mathrm{right}(i) > \mathrm{left}(i) \ge n$.  In other words,
+only nodes of indices less than $\lfloor n/2\rfloor$ have children.
+Therefore, a heap could be constructed as follows
+\begin{verbatim}
+// ...
+public class Heap<T extends Comparable<? super T>>
+{
+  // ...
+  public Heap(List<T> a)
+  {
+    list = a;
+    size = a.size();
+    for (int i = size >> 1; i-- > 0;)
+      heapify(i);
+  }
+}
+\end{verbatim}
+
+Before the construction, each node from $\lfloor n/2\rfloor$ (\verb|size >> 2|)
+to $n - 1$ is a leaf and a trivial heap on its own.  Consider the iteration
+where \verb|heapify| is called on node $i$ and assume every node after $i$
+is the root of a heap beforehand, then after the iteration, all nodes from $i$
+to $n - 1$ are foots of max-heaps.  Consequently, by mathematical induction,
+after the construction, the whole array becomes a heap.  According
+to~\cite[p. 159]{clrs}, this constructor runs in linear time ($O(n)$).
+
+Heapsort uses the max-heap to select the next largest element to move it
+to the start of the sorted region.  This in-place movement could be implemented
+as the method \verb|pop|, which also return the largest element to make
+the method make sense on its own.
+\begin{verbatim}
+// ...
+public class Heap<T extends Comparable<? super T>>
+{
+  // ...
+  public T pop() throws RuntimeException
+  {
+    if (size < 1)
+      throw new RuntimeException("heap underflow");
+    swap(list, 0, --size);
+    heapify(0);
+    return get(size);
+  }
+}
+\end{verbatim}
+
+Choosing the $n - 1$ largest element, we are left with the minimum value at
+the beginning of the list and the rest of the list are all greater or equal to
+the first element.
+\begin{verbatim}
+// ...
+public class Sort
+{
+  // ...
+  public static <T extends Comparable<? super T>>
+  void heap(List<T> list)
+  {
+    var heap = new Heap<T>(list);
+    for (int i = 1; i < list.size(); ++i)
+      heap.pop();
+  }
+}
+\end{verbatim}
+
+The step-by-step selection from the example heap is shown below as
+an illustration.  One may notice that the result qualifies as a min-heap.
+\begin{center}
+  \begin{forest}
+    for tree={circle,draw}
+    [,phantom [9 [6 [0] [4]] [8 [3] [,phantom]]]
+              [8 [6 [0] [4]] [3 [9,edge=dotted] [,phantom]]]
+              [6 [4 [0] [8,edge=dotted]] [3 [9,edge=dotted] [,phantom]]]]
+  \end{forest}
+\end{center}
+\begin{center}
+  \begin{forest}
+    for tree={circle,draw}
+    [,phantom [4 [0 [6,edge=dotted] [8,edge=dotted]]
+                 [3 [9,edge=dotted] [,phantom]]]
+              [3 [0 [6,edge=dotted] [8,edge=dotted]]
+                 [4,edge=dotted [9,edge=dotted] [,phantom]]]
+              [0 [3,edge=dotted [6,edge=dotted] [8,edge=dotted]]
+                 [4,edge=dotted [9,edge=dotted] [,phantom]]]]
+  \end{forest}
+\end{center}
+
+The running time of \verb|Sort.heap| is that of \verb|Heap| constructor,
+plus $n - 1$ times that of \verb|Heap.pop|, which is
+\begin{align*}
+  T(n) &= O(n) + (n - 1)(\Theta(1) + O(\log_2 n))\\
+       &= O(n) + \Theta(n)O(\log_2 n)\\
+       &= O(n) + O(n\log_2 n)\\
+       &= O(n\log_2 n)
+\end{align*}
+This is a huge improvement from selection sort's and bubble sort's $O(n^2)$.
+\pagebreak
+
+\section{Comparing}\label{sec:cmp}
+Our implementations of searching and sorting algorithms in Java work on
+any collection of data whose \emph{natural} order is specified, that is,
+where elements implement \verb|Comparable|.  However, they does not cover
+the case \emph{another} order is required, there is not any option to use
+our current library other than subclassing every item with a different
+\verb|compareTo| method, which, in every sense, is counter-intuitive.
+
+In~\cite{wu}, Wu dedicated a whole ``Sample Development'' section to address
+this issue and came up with the final solution of using the standard interface
+\verb|java.util.Comparator|~\cite{cmp} which declare the method \verb|compare|.
+We start with refactoring \verb|Sort.selection| to comply with this facility:
+\begin{verbatim}
+// ...
+import java.util.Comparator;
+
+public class Sort
+{
+  public static <T>
+  void selection(List<T> list, Comparator<T> comparator)
+  {
+    int i, j, m, n = list.size();
+    for (i = 0; i < n; ++i)
+      {
+        for (m = j = i; j < n; ++j)
+          if (comparator.compare(list.get(j), list.get(m)) < 0)
+            m = j;
+        swap(list, i, m);
+      }
+  }
+}
+\end{verbatim}
+
+To sort in reversed order, we can subclass \verb|Comparator|
+anonymously~\cite{anon}
+\begin{verbatim}
+var list = java.util.Arrays.asList(4, 2, 0, 6, 9);
+Sort.selection(list, new java.util.Comparator<Integer>()
+{
+  public int compare(Integer a, Integer b)
+  {
+    return -a.compareTo(b);
+  }
+});
+System.out.println(list);
+\end{verbatim}
+
+As expected, the snippet above prints \verb|[9, 6, 4, 2, 0]| to \verb|stdout|.
+
+In order to maintain backward-comparability, we write a helper class extracting
+the natural order from any \verb|Comparable| to a \verb|Comparator|:
+\begin{verbatim}
+import java.util.Comparator;
+
+public class Compare<T extends Comparable<? super T>>
+implements Comparator<T>
+{
+  public int compare(T a, T b)
+  {
+    return a.compareTo(b);
+  }
+}
+\end{verbatim}
+and wrap the current \verb|Sort.selection| with
+\begin{verbatim}
+// ...
+public class Sort
+{
+  // ...
+  public static <T extends Comparable<? super T>>
+  void selection(List<T> list)
+  {
+    selection(list, new Compare<T>());
+  }
+}
+\end{verbatim}
+
+\verb|Sort.bubble| can be refactored similarly, but since \verb|Sort.heap|
+does all the comparisons in \verb|Heap|, we are required to make \verb|Heap|
+work with \verb|Comparator|'s
+\begin{verbatim}
+// ...
+import java.util.Comparator;
+
+public class Heap<T>
+{
+  // ...
+  private Comparator<T> cmp;
+
+  public void heapify(int i)
+  {
+    int right = i + 1 << 1;
+    int left = right - 1;
+    int largest = i;
+    if (left < size && cmp.compare(get(left), get(largest)) > 0)
+      largest = left;
+    if (right < size && cmp.compare(get(right), get(largest)) > 0)
+      largest = right;
+    if (largest != i)
+      {
+        swap(list, i, largest);
+        heapify(largest);
+      }
+  }
+
+  public Heap(List<T> a, Comparator<T> c)
+  {
+    list = a;
+    size = a.size();
+    cmp = c;
+    for (int i = size >> 1; i-- > 0;)
+      heapify(i);
+  }
+}
+\end{verbatim}
+and re-write \verb|Sort.heap| to use the new \verb|Heap|
+\begin{verbatim}
+// ...
+public class Sort
+{
+  // ...
+  public static <T>
+  void heap(List<T> list, Comparator<T> comparator)
+  {
+    var heap = new Heap<T>(list, comparator);
+    for (int i = 1; i < list.size(); ++i)
+      heap.pop();
+  }
+
+  public static <T extends Comparable<? super T>>
+  void heap(List<T> list)
+  {
+    heap(list, new Compare<T>());
+  }
+}
+\end{verbatim}
+
+For the next example, we use a minimal, read-only version of the \verb|Person|
+class from~\cite[p. 666]{wu}, which is ordered by \verb|name| by default:
+\begin{verbatim}
+public class Person implements Comparable<Person>
+{
+  private String name;
+  private Integer age;
+  private Character gender;
+
+  public Person(String name, Integer age, Character gender)
+  {
+    this.name = name;
+    this.age = age;
+    this.gender = gender;
+  }
+
+  public int compareTo(Person other)
+  {
+    return this.name.compareTo(other.name);
+  }
+
+  public String toString()
+  {
+    return String.format("%s (%d%c)", name, age, gender);
+  }
+
+  public String getName()
+  {
+    return name;
+  }
+
+  public Integer getAge()
+  {
+    return age;
+  }
+ 
+  public Character getGender()
+  {
+    return gender;
+  }
+}
+\end{verbatim}
+
+We use a list of the oldest current state leaders~\cite{old} for this test
+\begin{verbatim}
+var list = java.util.Arrays.asList(
+  new Person("Mahathir Mohamad", 94, 'M'),
+  new Person("Elizabeth II", 93, 'F'),
+  new Person("Sheikh Sabah Al-Ahmad Al-Jaber Al-Sabah", 90, 'M'),
+  new Person("Paul Biya", 86, 'M'),
+  new Person("Michel Aoun", 84, 'M'),
+  new Person("Mahmoud Abbas", 83, 'M'),
+  new Person("Francis", 82, 'M'));
+Sort.heap(list);
+list.forEach(System.out::println);
+\end{verbatim}
+and get
+\begin{verbatim}
+Elizabeth II (93F)
+Francis (82M)
+Mahathir Mohamad (94M)
+Mahmoud Abbas (83M)
+Michel Aoun (84M)
+Paul Biya (86M)
+Sheikh Sabah Al-Ahmad Al-Jaber Al-Sabah (90M)
+\end{verbatim}
+
+It would neither be challenging to re-sort this list by their ages:
+\begin{verbatim}
+var ageComparator = new java.util.Comparator<Person>()
+{
+  public int compare(Person a, Person b)
+  {
+    return a.getAge().compareTo(b.getAge());
+  }
+};
+Sort.heap(list, ageComparator);
+list.forEach(System.out::println);
+\end{verbatim}
+which gives us
+\begin{verbatim}
+Francis (82M)
+Mahmoud Abbas (83M)
+Michel Aoun (84M)
+Paul Biya (86M)
+Sheikh Sabah Al-Ahmad Al-Jaber Al-Sabah (90M)
+Elizabeth II (93F)
+Mahathir Mohamad (94M)
+\end{verbatim}
+
+Linear search is able to run without any modification: we would still receive
+4 from \verb|Search.linear(list, list.get(4))|.  Binary search, however,
+would not work correctly if the order of the list is not \emph{natural}.
+One with \verb|Comparator| support may be implemented as follows.
+\begin{verbatim}
+import java.util.List;
+import java.util.Comparator;
+
+public class Search
+{
+  // ...
+  private static <T>
+  int binary(List<? extends T> list, T key,
+             Comparator<? super T> c, int low, int high)
+  {
+    if (high < low)
+      return NOT_FOUND;
+    var mid = (low + high) / 2;
+    var cmp = c.compare(list.get(mid), key);
+    if (cmp < 0)
+      return binary(list, key, c, mid + 1, high);
+    if (cmp > 0)
+      return binary(list, key, c, low, mid - 1);
+    return mid;
+  }
+
+  public static <T>
+  int binary(List<? extends T> list, T key,
+             Comparator<? super T> c)
+  {
+    return binary(list, key, c, 0, list.size());
+  }
+}
+\end{verbatim}
+
+Now \verb|Search.binary(list, list.get(5), ageComparator)| would return
+the right index 5 instead of -1 like \verb|Search.binary(list, list.get(5))|.
+\pagebreak
+
+\section{Conclusion}
+Albeit searching and sorting belong to the category of algorithms,
+by implementing them, we were still able to recognize a variety of
+object-oriented concepts, namely:
+\begin{enumerate}
+  \item Through encapsulation of the inner representations
+    and behaviors, we can create intuitive programming interfaces,
+    whilst keeping the code clear and concise.  Notable examples are
+    the implementation of binary search and the heap data structure.
+  \item Through polymorphism, generic and convenient libraries can be written,
+    which allow more \emph{code reuse} and thus facilitate more effective
+    development.  We wrote all of the classes and methods with this principle
+    in mind.
+  \item Through inheritance, it is possible to extend the functionalities of
+    each object.  Together with polymorphism (which defines the behavioral
+    interfaces), it enable us to generalize our codebase one step further,
+    as shown in section~\ref{sec:cmp}, without spending too much energy
+    on refactoring.
+\end{enumerate}
+
+Generally, though, we find shoving every self-contained function into a class
+as a static method rather redundant.
+\pagebreak
+
+\begin{thebibliography}{99}
+  \bibitem{wu} C. Thomas Wu.
+    ``Chapter 11: Sorting and Searching''.
+    \emph{An Introduction to Object-Oriented Programming with Java}, 5 ed.
+    McGraw-Hill, 2010.  ISBN 978–0–07–352330–9.
+  \bibitem{list} \href{https://docs.oracle.com/javase/8/docs/api/java/util/List.html}{List (Java Platform SE 8)}.
+    \emph{Oracle}.
+  \bibitem{var} \href{http://openjdk.java.net/jeps/286}{JEP 286: Local-Variable Type Inference}.
+    \emph{OpenJDK}.
+  \bibitem{bsearch} \href{http://mathworld.wolfram.com/BinarySearch.html}{Binary Search}.
+    \emph{Wolfram WathWorld}.
+  \bibitem{infer} \href{https://docs.oracle.com/javase/tutorial/java/generics/methods.html}{Generic Methods}.
+    \emph{Oracle}.
+  \bibitem{collections} \href{https://docs.oracle.com/javase/8/docs/api/java/util/Collections.html}{Collections (Java Platform SE 8)}.
+    \emph{Oracle}.
+  \bibitem{clrs} Thomas H. Cormen, Charles E. Leiserson,
+                 Ronald L. Rivest and Clifford Stein.
+    \emph{Introduction to Algorithms}, 3 ed.
+    MIT Press, 2009.  ISBN 978-0-262-03384-8.
+  \bibitem{bubblebad} Owen Astrachan.
+    \emph{\href{https://users.cs.duke.edu/~ola/bubble/bubble.html}{Bubble Sort: An Archaeological Algorithmic Analysis}}.
+    Duke University.
+  \bibitem{wikibubble} \href{https://en.wikipedia.org/wiki/Bubble_sort#Optimizing_bubble_sort}{Bubble sort}.
+    \emph{Wikipedia}.
+    Section 2.2: \emph{Optimizing bubble sort}.
+  \bibitem{peculiar} Donald E. Knuth.  The Dangers of Computer-Science Theory.
+    \emph{Studies in Logic and the Foundations of Mathematics}, vol. 74.
+    Elsevier, 1973.
+    doi:\href{https://doi.org/10.1016/S0049-237X(09)70357-X}{10.1016/S0049-237X(09)70357-X}.
+  \bibitem{heapselect} Steven Skiena.
+    ``Searching and Sorting''.
+    \emph{The Algorithm Design Manual}, p. 109.
+    Springer, 2008.
+    doi:\href{https://doi.org/10.1007/978-1-84800-070-4_4}{10.1007/978-1-84800-070-4{\_}4}.
+    ISBN 978-1-84800-069-8.
+  \bibitem{cmp} \href{https://docs.oracle.com/javase/8/docs/api/java/util/mparator.html}{Comparator (Java Platform SE 8)}.
+    \emph{Oracle}.
+  \bibitem{anon} \href{https://docs.oracle.com/javase/tutorial/java/javaOO/anonymousclasses.html}{Anonymous Classes}.
+    \emph{Oracle}.
+  \bibitem{old} \href{https://en.wikipedia.org/wiki/Lists_of_state_leaders_by_age#10_oldest_currently_serving_state_leaders}{Lists of state leaders by age}.
+    \emph{Wikipedia}.
+    Section 1: \emph{10 oldest currently serving state leaders}.
+\end{thebibliography}
+\end{document}
diff --git a/usth/ICT2.2/midterm/slides/USTH.jpg b/usth/ICT2.2/midterm/slides/USTH.jpg
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@@ -0,0 +1,734 @@
+\documentclass[pdf]{beamer}
+\usepackage[english,vietnamese]{babel}
+\usepackage{amsmath}
+\usepackage{booktabs}
+\usepackage{colortbl}
+\usepackage{graphicx}
+\usepackage{hyperref}
+\usepackage{lmodern}
+\usepackage{forest}
+
+\mode<presentation>{}
+\usetheme[hideothersubsections]{Hannover}
+\usefonttheme[onlymath]{serif}
+\usebackgroundtemplate{
+  \includegraphics[width=\paperwidth,height=\paperheight]{USTH.jpg}}
+\beamerdefaultoverlayspecification{<+->}
+
+\title[Sort \& Search]{Sorting and Searching}
+\author[Group 11]{Nguyễn Công Thành---BI9-210\\
+                  Nguyễn Gia Phong---BI9-184\\
+                  Nguyễn Văn Tùng---BI9-229\\
+                  Trần Minh Vương---BI9-239\\
+                  Trần Hồng Minh---BI8-114}
+\institute{University of Science and Technology of Hà Nội}
+\date{\selectlanguage{english}\today}
+
+\begin{document}
+\frame{\titlepage}
+\begin{frame}{Contents}
+  \tableofcontents
+\end{frame}
+
+\section{Introduction}
+\begin{frame}{Introduction}\Large
+  \begin{itemize}
+    \item Sorting \& Searching are \emph{important}
+    \item Object-Oriented Programming
+    \item Implementation in Java
+    \item Generic Programming
+  \end{itemize}
+\end{frame}
+
+\section{Searching}
+\begin{frame}[fragile]{Searching}\Large
+  Given a value $x$, return the [zero-based] index of $x$ in the array,
+  if such $x$ exists.  Otherwise, return \verb|NOT_FOUND| (-1).
+\end{frame}
+
+\subsection{Linear Search}
+\begin{frame}[fragile]{Linear Search}\Large
+  \begin{itemize}
+    \item Checks sequentially till
+      \begin{itemize}\Large
+        \item match found
+        \item whole list searched
+      \end{itemize}
+    \item Linear time complexity
+    \item \verb|java.util.List.indexOf|
+    \item Example: Search for number 7
+      \begin{center}
+        \only<1-5>{\begin{tabular}{|c|c|c|c|c|}
+          \hline 4 & 20 & 6 & 9\\\hline
+        \end{tabular}}%
+        \only<6>{\begin{tabular}{|c|c|c|c|c|}
+          \hline \cellcolor{yellow}4 & 20 & 6 & 9\\\hline
+        \end{tabular}}%
+        \only<7>{\begin{tabular}{|c|c|c|c|c|}
+          \hline 4 & \cellcolor{yellow}20 & 6 & 9\\\hline
+        \end{tabular}}%
+        \only<8>{\begin{tabular}{|c|c|c|c|c|}
+          \hline 4 & 20 & \cellcolor{yellow}6 & 9\\\hline
+        \end{tabular}}%
+        \only<9>{\begin{tabular}{|c|c|c|c|c|}
+          \hline 4 & 20 & 6 & \cellcolor{yellow}9\\\hline
+        \end{tabular}}
+      \end{center}
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Implementation}
+\begin{verbatim}
+import java.util.List;
+
+public class Search
+{
+  public static final int NOT_FOUND = -1;
+
+  public static linear(List l, Object o)
+  {
+    for (int i = 0; i < l.size(); ++i)
+      if (o == null ? l.get(i) == null
+                    : o.equals(l.get(i)))
+        return i;
+    return NOT_FOUND;
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\subsection{Binary Search}
+\begin{frame}[fragile]{Binary Search}\Large
+  \begin{itemize}
+    \item For sorted arrays only
+    \item Repeat halving interval cannot have $x$ till
+      \begin{itemize}\Large
+        \item match found
+        \item invalid interval
+      \end{itemize}
+    \item Logarithmic time complexity
+    \item \verb|java.util.Collections.binarySearch|
+    \item Example: Search for number 7
+      \begin{center}
+        \only<1-6>{\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|}
+          \hline 0 & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & $\emptyset$\\\hline
+        \end{tabular}}%
+        \only<7>{\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|}
+          \hline \cellcolor{red}0 & 1 & 2 & 3 & 4 & \cellcolor{green}5
+          & 6 & 7 & 8 & 9 & \cellcolor{blue}$\emptyset$\\\hline
+        \end{tabular}}%
+        \only<8>{\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|}
+          \hline 0 & 1 & 2 & 3 & 4 & 5 & \cellcolor{red}6 & 7
+          & \cellcolor{green}8 & 9 & \cellcolor{blue}$\emptyset$\\\hline
+        \end{tabular}}%
+        \only<9>{\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|}
+          \hline 0 & 1 & 2 & 3 & 4 & 5 & \cellcolor{yellow}6 & \cellcolor{blue}7
+          & 8 & 9 & $\emptyset$\\\hline
+        \end{tabular}}%
+        \only<10>{\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|}
+          \hline 0 & 1 & 2 & 3 & 4 & 5 & 6 & \cellcolor{gray}7
+          & 8 & 9 & $\emptyset$\\\hline
+        \end{tabular}}
+      \end{center}
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Implementation}
+\begin{verbatim}
+public class Search
+{
+  private static <T> int binary(
+    List<? extends Comparable<? super T>> list,
+    T key, int low, int high)
+  {
+    if (high < low)
+      return NOT_FOUND;
+    var mid = (low + high) / 2;
+    var cmp = list.get(mid).compareTo(key);
+    if (cmp < 0)
+      return binary(list, key, mid + 1, high);
+    if (cmp > 0)
+      return binary(list, key, low, mid - 1);
+    return mid;
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Wrapper}
+\begin{verbatim}
+public class Search
+{
+  public static <T> int binary(
+    List<? extends Comparable<? super T>> list,
+    T key)
+  {
+    return binary(list, key, 0, list.size());
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\section{Sorting}
+\begin{frame}{Sorting}\Large
+  Given an array of $n$ values, arrange the values into ascending order.
+\end{frame}
+
+\subsection{Selection Sort}
+\begin{frame}{Selection Sort}\Large
+  \begin{itemize}
+    \item Iterate through every position,\\
+      select the minimum from there to array's end
+    \item Quadratic time complexity
+    \item Example:
+      \only<1-2>{\begin{tabular}{|c|c|c|c|c|}
+        \hline 6 & 9 & 4 & 2 & 0\\\hline
+      \end{tabular}}%
+      \only<3>{\begin{tabular}{|c|c|c|c|c|}
+        \hline 6 & 9 & 4 & 2 & \cellcolor{yellow}0\\\hline
+      \end{tabular}}%
+      \only<4>{\begin{tabular}{|c|c|c|c|c|}
+        \hline \cellcolor{gray}0 & 9 & 4 & \cellcolor{yellow}2 & 6\\\hline
+      \end{tabular}}%
+      \only<5>{\begin{tabular}{|c|c|c|c|c|}
+        \hline \cellcolor{gray}0 & \cellcolor{gray}2 &
+        \cellcolor{yellow}4 & 9 & 6\\\hline
+      \end{tabular}}%
+      \only<6>{\begin{tabular}{|c|c|c|c|c|}
+        \hline \cellcolor{gray}0 & \cellcolor{gray}2 &
+        \cellcolor{gray}4 & 9 & \cellcolor{yellow}6\\\hline
+      \end{tabular}}%
+      \only<7>{\begin{tabular}{|c|c|c|c|c|}
+        \hline \cellcolor{gray}0 & \cellcolor{gray}2 &
+        \cellcolor{gray}4 & \cellcolor{gray}6 & \cellcolor{yellow}9\\\hline
+      \end{tabular}}%
+      \only<8>{\begin{tabular}{|c|c|c|c|c|}
+        \hline\rowcolor{gray} 0 & 2 & 4 & 6 & 9\\\hline
+      \end{tabular}}
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile,label=selimpl]{Implementation}
+\begin{verbatim}
+import static java.util.Collections.swap;
+
+public class Sort
+{
+  public static <T extends Comparable<? super T>>
+  void selection(List<T> list)
+  {
+    int i, j, m, n = list.size();
+    for (i = 0; i < n; ++i)
+      {
+        for (m = j = i; j < n; ++j)
+          if (list.get(j).compareTo(list.get(m)) < 0)
+            m = j;
+        swap(list, i, m);
+      }
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\subsection{Bubble Sort}
+\begin{frame}{Bubble Sort}\Large
+  \begin{itemize}
+    \item Repeatedly iterate through the array,\\
+      swap adjacent elements in wrong order
+    \item Quadratic time complexity
+    \item Example:
+      \only<1-2>{\begin{tabular}{|c|c|c|c|c|}
+        \hline 6 & 9 & 4 & 2 & 0\\\hline
+      \end{tabular}}%
+      \only<3>{\begin{tabular}{|c|c|c|c|c|}
+        \hline \cellcolor{magenta}6 & \cellcolor{yellow}9 & 4 & 2 & 0\\\hline
+      \end{tabular}}%
+      \only<4>{\begin{tabular}{|c|c|c|c|c|}
+        \hline 6 & \cellcolor{magenta}9 & \cellcolor{yellow}4 & 2 & 0\\\hline
+      \end{tabular}}%
+      \only<5>{\begin{tabular}{|c|c|c|c|c|}
+        \hline 6 & 4 & \cellcolor{magenta}9 & \cellcolor{yellow}2 & 0\\\hline
+      \end{tabular}}%
+      \only<6>{\begin{tabular}{|c|c|c|c|c|}
+        \hline 6 & 4 & 2 & \cellcolor{magenta}9 & \cellcolor{yellow}0\\\hline
+      \end{tabular}}%
+      \only<7>{\begin{tabular}{|c|c|c|c|c|}
+        \hline \cellcolor{magenta}6 & \cellcolor{yellow}4
+        & 2 & 0 & \cellcolor{gray}9\\\hline
+      \end{tabular}}%
+      \only<8>{\begin{tabular}{|c|c|c|c|c|}
+        \hline 4 & \cellcolor{magenta}6 & \cellcolor{yellow}2
+        & 0 & \cellcolor{gray}9\\\hline
+      \end{tabular}}%
+      \only<9>{\begin{tabular}{|c|c|c|c|c|}
+        \hline 4 & 2 & \cellcolor{magenta}6 & \cellcolor{yellow}0
+        & \cellcolor{gray}9\\\hline
+      \end{tabular}}%
+      \only<10>{\begin{tabular}{|c|c|c|c|c|}
+        \hline \cellcolor{magenta}4 & \cellcolor{yellow}2 & 0
+        & \cellcolor{gray}6 & \cellcolor{gray}9\\\hline
+      \end{tabular}}%
+      \only<11>{\begin{tabular}{|c|c|c|c|c|}
+        \hline 2 & \cellcolor{magenta}4 & \cellcolor{yellow}0
+        & \cellcolor{gray}6 & \cellcolor{gray}9\\\hline
+      \end{tabular}}%
+      \only<12>{\begin{tabular}{|c|c|c|c|c|}
+        \hline \cellcolor{magenta}2 & \cellcolor{yellow}0
+        & \cellcolor{gray}4 & \cellcolor{gray}6 & \cellcolor{gray}9\\\hline
+      \end{tabular}}%
+      \only<13>{\begin{tabular}{|c|c|c|c|c|}
+        \hline\rowcolor{gray} 0 & 2 & 4 & 6 & 9\\\hline
+      \end{tabular}}
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Implementation}
+\begin{verbatim}
+public class Sort
+{
+  public static <T extends Comparable<? super T>>
+  void bubble(List<T> list)
+  {
+    for (int n = list.size(), m = 0;
+         n > 1; n = m, m = 0)
+      for (int i = 1; i < n; ++i)
+        if (list.get(i).compareTo(list.get(i-1)) < 0)
+          swap(list, m = i, i - 1);
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\begin{frame}{Bubble v Selection: Dawn of Sort}\Large
+  \only<1>{
+    C. Thomas Wu (2010) claimed that
+    \begin{quote}
+      On average, we expect the bubble sort to finish sorting sooner than
+      the selection sort, \emph{because there will be more data movements for
+      the same number of comparisons}, and there is a test to exit the method
+      when the array gets sorted.
+    \end{quote}}
+  \only<2>{\includegraphics[width=\textwidth]{squint.jpg}}
+\end{frame}
+
+\begin{frame}{BvS: Time Complexity}
+  \begin{center}
+    \begin{tabular}{c c c c c}
+      \toprule
+      Case & \multicolumn{2}{c}{Selection Sort}
+           & \multicolumn{2}{c}{Bubble Sort}\\
+      \midrule
+      & Comparisons & Swaps & Comparisons & Swaps\\
+      Best & $\Omega(n^2)$ & $\Omega(n)$ & $\Omega(n)$ & $\Omega(n)$\\
+      Average & $\Theta(n^2)$ & $\Theta(n)$ & $\Theta(n^2)$ & $\Theta(n^2)$\\
+      Worst & $O(n^2)$ & $O(n)$ & $O(n^2)$ & $O(n^2)$\\
+      \bottomrule
+    \end{tabular}
+  \end{center}
+\end{frame}
+
+\begin{frame}{BvS: Average Case in Practice}
+  \begin{center}
+    \includegraphics[width=0.85\textwidth]{bubbleplot.jpg}
+  \end{center}
+\end{frame}
+
+\subsection{Heapsort}
+\begin{frame}{Heapsort}\Large
+  \begin{itemize}
+    \item Selection sort, but use heap for selection
+    \item Linearithmic time complexity
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Using PriorityQueue (Min-Heap)}
+\begin{verbatim}
+import java.util.PriorityQueue;
+
+public class Sort
+{
+  public static <T extends Comparable<? super T>>
+  void pq(List<T> list)
+  {
+    var q = new PriorityQueue<T>(list);
+    for (int i = 0; i < list.size(); ++i)
+      list.set(i, q.poll());
+  }
+}
+\end{verbatim}\pause
+
+But hey, there is also \verb|List.sort|!
+\end{frame}
+
+\begin{frame}{Binary Max-Heap}\Large
+  \begin{itemize}
+    \item Nearly complete binary tree
+    \item Parent $\ge$ Children $\Longrightarrow$ Root is max!
+    \item Example:
+      \begin{center}
+        \begin{forest}
+          for tree={circle,draw}
+          [9 [4 [0] [6]] [8 [3] [,phantom]]]
+        \end{forest}
+      \end{center}
+  \end{itemize}
+\end{frame}
+
+\begin{frame}{Linear Binary Max-Heap}\Large
+  \begin{itemize}
+    \item $length$ of inner representation
+    \item $size$ of heap ($0 \le size \le length$)
+    \item Index within $[0\,..\, size)$
+      \[\begin{array}{ll}
+        \mathrm{parent}(i) &= \left\lfloor\dfrac{i - 1}{2}\right\rfloor\\
+        \mathrm{left}(i) &= 2i + 1\\
+        \mathrm{right}(i) &= 2i + 2
+      \end{array}\]
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Heap Declaration}
+\begin{verbatim}
+public class Heap<T extends Comparable<? super T>>
+{
+  private List<T> list;
+  private int size;
+
+  public int getSize() { return size; }
+  public int getLength() { return list.size(); }
+  public T get(int i) { return list.get(i); }
+}
+\end{verbatim}
+\end{frame}
+
+\begin{frame}[fragile]{void Heap::heapify(int i)}
+\begin{verbatim}
+int right = i + 1 << 1;
+int left = right - 1;
+int largest = i;
+if (left < size
+    && get(left).compareTo(get(largest)) > 0)
+  largest = left;
+if (right < size
+    && get(right).compareTo(get(largest)) > 0)
+  largest = right;
+if (largest != i)
+  {
+    swap(list, i, largest);
+    heapify(largest);
+  }
+\end{verbatim}
+\end{frame}
+
+\begin{frame}{Heapification}\huge
+  \begin{center}
+    \only<1>{\begin{forest}
+      for tree={circle,draw}
+      [4,fill=yellow [9 [0] [6]] [8 [3] [,phantom]]]
+    \end{forest}}%
+    \only<2>{\begin{forest}
+      for tree={circle,draw}
+      [9 [4,fill=yellow [0] [6]] [8 [3] [,phantom]]]
+    \end{forest}}%
+    \only<3>{\begin{forest}
+      for tree={circle,draw}
+      [9 [6 [0] [4,fill=yellow]] [8 [3] [,phantom]]]
+    \end{forest}}
+  \end{center}
+\end{frame}
+
+\begin{frame}[fragile]{The Loop Invariant}\Large
+  For $i$ =$\lfloor n/2\rfloor - 1$ downto $0$, \verb|heapify(i)|:
+  \begin{itemize}
+    \item \textbf{Initialization}: For every array,
+      each node $\lfloor n/2\rfloor\,..\,n-1$ is trival max-heap (leaf).
+    \item \textbf{Maintenance}: If nodes $i+1\,..\,n-1$ are max-heaps,
+      after \verb|heapify(i)|, all nodes $i\,..\,n-1$ are max-heaps.
+    \item \textbf{Terminination}: After \verb|heapify(0)|,
+      the whole array is a max-heap.
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Heap Constructor}
+\begin{verbatim}
+public class Heap<T extends Comparable<? super T>>
+{
+  public Heap(List<T> a)
+  {
+    list = a;
+    size = a.size();
+    for (int i = size >> 1; i-- > 0;)
+      heapify(i);
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Maximum Selection}
+\begin{verbatim}
+public class Heap<T extends Comparable<? super T>>
+{
+  public T pop() throws RuntimeException
+  {
+    if (size < 1)
+      throw new RuntimeException("heap underflow");
+    swap(list, 0, --size);
+    heapify(0);
+    return get(size);
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Heapsort Implementation}
+\begin{verbatim}
+public class Sort
+{
+  public static <T extends Comparable<? super T>>
+  void heap(List<T> list)
+  {
+    var heap = new Heap<T>(list);
+    for (int i = 1; i < list.size(); ++i)
+      heap.pop();
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\begin{frame}{Sorting a Heap}\huge
+  \begin{center}
+    \only<1>{\begin{forest}
+      for tree={circle,draw}
+      [9 [6 [0] [4]] [8 [3] [,phantom]]]\
+    \end{forest}}%
+    \only<2>{\begin{forest}
+      for tree={circle,draw}
+      [8 [6 [0] [4]] [3 [9,edge=dashed] [,phantom]]]
+    \end{forest}}%
+    \only<3>{\begin{forest}
+      for tree={circle,draw}
+      [6 [4 [0] [8,edge=dashed]] [3 [9,edge=dashed] [,phantom]]]
+    \end{forest}}%
+    \only<4>{\begin{forest}
+      for tree={circle,draw}
+      [4 [0 [6,edge=dashed] [8,edge=dashed]]
+         [3 [9,edge=dashed] [,phantom]]]
+    \end{forest}}%
+    \only<5>{\begin{forest}
+      for tree={circle,draw}
+      [3 [0 [6,edge=dashed] [8,edge=dashed]]
+         [4,edge=dashed [9,edge=dashed] [,phantom]]]
+    \end{forest}}%
+    \only<6>{\begin{forest}
+      for tree={circle,draw}
+      [0 [3,edge=dashed [6,edge=dashed] [8,edge=dashed]]
+         [4,edge=dashed [9,edge=dashed] [,phantom]]]
+    \end{forest}}%
+  \end{center}
+\end{frame}
+
+\section{Comparing}
+\begin{frame}[fragile]{Comparing}\Large
+  \begin{itemize}
+    \item $<$, $\le$, $=$, $\ge$, $>$ or $\ne$?
+    \item e.g. \verb|420 > 69|
+    \item But \verb|"420" < "69"|!
+    \item How do we sort any collection of data?
+  \end{itemize}
+\end{frame}
+
+\subsection{Comparable}
+\begin{frame}[fragile]{Comparable}\Large
+  \begin{itemize}
+    \item \emph{Natural} increasing order
+    \item Define \verb|int compareTo(T other)|
+    \item Negative: less than; Zero: equal;\\
+      Positve: greater than.
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Example Element}
+\begin{verbatim}
+public class Person implements Comparable<Person>
+{
+  private String name;
+  private Integer age;
+  private Character gender;
+
+  public int compareTo(Person other)
+  {
+    return this.name.compareTo(other.name);
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Example Element (misc.)}
+\begin{verbatim}
+public class Person implements Comparable<Person>
+{
+  public Person(String name, Integer age,
+                Character gender)
+  {
+    this.name = name;
+    this.age = age;
+    this.gender = gender;
+  }
+
+  public String toString()
+  {
+    return String.format("%s (%d%c)",
+                         name, age, gender);
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\againframe{selimpl}
+
+\begin{frame}[fragile]{Sorting People}
+\begin{verbatim}
+var list = java.util.Arrays.asList(
+  new Person("Mahathir Mohamad", 94, 'M'),
+  new Person("Elizabeth II", 93, 'F'),
+  new Person("Paul Biya", 86, 'M'),
+  new Person("Michel Aoun", 84, 'M'),
+  new Person("Mahmoud Abbas", 83, 'M'),
+  new Person("Francis", 82, 'M'));
+Sort.selection(list);
+list.forEach(System.out::println);
+\end{verbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Sort by Name Output}\Large
+  \begin{quote}
+    Elizabeth II (93F)\\
+    Francis (82M)\\
+    Mahathir Mohamad (94M)\\
+    Mahmoud Abbas (83M)\\
+    Michel Aoun (84M)\\
+    Paul Biya (86M)
+  \end{quote}
+\end{frame}
+
+\subsection{Comparator}
+\begin{frame}[fragile]{Comparator}\Large
+  \begin{itemize}
+    \item How about reverse order?
+    \item Sort by another \emph{key}?
+    \item \verb|compareTo| (or any other) method\\
+      cannot be overriden without subclassing.
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{java.util.Comparator}\Large
+  \begin{itemize}
+    \item Define \verb|int compare(T one, T another)|
+    \item Negative: less than; Zero: equal;\\
+      Positve: greater than.
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]{Refactored Selection Sort}
+\begin{verbatim}
+public class Sort
+{
+  public static <T>
+  void selection(List<T> list,
+                 Comparator<T> comparator)
+  {
+    int i, j, m, n = list.size();
+    for (i = 0; i < n; ++i)
+      {
+        for (m = j = i; j < n; ++j)
+          if (comparator.compare(list.get(j),
+                                 list.get(m)) < 0)
+            m = j;
+        swap(list, i, m);
+      }
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Exposing Attributes}
+\begin{verbatim}
+public class Person implements Comparable<Person>
+{
+  public String getName() { return name; }
+  public Integer getAge() { return age; }
+  public Character getGender() { return gender; }
+}
+\end{verbatim}
+\end{frame}
+
+\begin{frame}[fragile]{Sorting by Age}
+\begin{verbatim}
+Sort.heap(list, new Comparator<Person>()
+{
+  public int compare(Person a, Person b)
+  {
+    return a.getAge().compareTo(b.getAge());
+  }
+});
+list.forEach(System.out::println);
+\end{verbatim}
+\end{frame}
+
+\begin{frame}{Sorting by Age Output}\Large
+  \begin{quote}
+    Francis (82M)\\
+    Mahmoud Abbas (83M)\\
+    Michel Aoun (84M)\\
+    Paul Biya (86M)\\
+    Elizabeth II (93F)\\
+    Mahathir Mohamad (94M)
+  \end{quote}
+\end{frame}
+
+\begin{frame}[fragile]{Backward Compatibility}
+\begin{verbatim}
+public class Compare<T extends Comparable<? super T>>
+implements Comparator<T>
+{
+  public int compare(T a, T b)
+  {
+    return a.compareTo(b);
+  }
+}
+
+public class Sort
+{
+  public static <T extends Comparable<? super T>>
+  void selection(List<T> list)
+  {
+    selection(list, new Compare<T>());
+  }
+}
+\end{verbatim}
+\end{frame}
+
+\section{Conclusion}
+\begin{frame}{Conclusion}\Large
+  Though the topic is more algorithmic than OOP:
+  \begin{itemize}
+    \item \textbf{Encapsulation}: Intuitive interface and concise code,
+      e.g. binary search, heap.
+    \item \textbf{Polymorphism}: Generic, convenient libraries,
+      thus more \emph{code reuse} and more effective development.
+    \item \textbf{Inheritance}: Extend objects' functionalities,
+      hence even more generalization.
+    \item However, shoving every self-contained function into a class
+      is rather redundant.
+  \end{itemize}
+\end{frame}
+
+\begin{frame}{Copying}\Large
+  \begin{itemize}
+    \item For the list of references, see our report.
+    \item The report also contains more explainations and examples.
+    \item The documents as well as Java source files are licensed under
+      \href{https://creativecommons.org/licenses/by-sa/4.0/}{CC BY-SA 4.0}.
+  \end{itemize}
+\end{frame}
+\end{document}
diff --git a/usth/ICT2.2/midterm/slides/squint.jpg b/usth/ICT2.2/midterm/slides/squint.jpg
new file mode 100644
index 0000000..1e86257
--- /dev/null
+++ b/usth/ICT2.2/midterm/slides/squint.jpg
Binary files differdiff --git a/usth/ICT2.2/midterm/src/Compare.java b/usth/ICT2.2/midterm/src/Compare.java
new file mode 100644
index 0000000..e6bda90
--- /dev/null
+++ b/usth/ICT2.2/midterm/src/Compare.java
@@ -0,0 +1,9 @@
+import java.util.Comparator;
+
+public class Compare<T extends Comparable<? super T>> implements Comparator<T>
+{
+  public int compare(T a, T b)
+  {
+    return a.compareTo(b);
+  }
+}
diff --git a/usth/ICT2.2/midterm/src/Heap.java b/usth/ICT2.2/midterm/src/Heap.java
new file mode 100644
index 0000000..3803924
--- /dev/null
+++ b/usth/ICT2.2/midterm/src/Heap.java
@@ -0,0 +1,61 @@
+import java.util.List;
+import java.util.Comparator;
+
+import static java.util.Collections.swap;
+
+public class Heap<T>
+{
+  private List<T> list;
+  private Comparator<T> cmp;
+  private int size;
+
+  public int getSize()
+  {
+    return size;
+  }
+
+  public int getLength()
+  {
+    return list.size();
+  }
+
+  public T get(int i)
+  {
+    return list.get(i);
+  }
+
+  public void heapify(int i)
+  {
+    int right = i + 1 << 1;
+    int left = right - 1;
+    int largest = i;
+
+    if (left < size && cmp.compare(get(left), get(largest)) > 0)
+      largest = left;
+    if (right < size && cmp.compare(get(right), get(largest)) > 0)
+      largest = right;
+    if (largest != i)
+      {
+        swap(list, i, largest);
+        heapify(largest);
+      }
+  }
+
+  public Heap(List<T> a, Comparator<T> c)
+  {
+    list = a;
+    size = a.size();
+    cmp = c;
+    for (int i = size >> 1; i-- > 0;)
+      heapify(i);
+  }
+
+  public T pop() throws RuntimeException
+  {
+    if (size < 1)
+      throw new RuntimeException("heap underflow");
+    swap(list, 0, --size);
+    heapify(0);
+    return get(size);
+  }
+}
diff --git a/usth/ICT2.2/midterm/src/Person.java b/usth/ICT2.2/midterm/src/Person.java
new file mode 100644
index 0000000..045c3f4
--- /dev/null
+++ b/usth/ICT2.2/midterm/src/Person.java
@@ -0,0 +1,38 @@
+public class Person implements Comparable<Person>
+{
+  private String name;
+  private Integer age;
+  private Character gender;
+
+  public Person(String name, Integer age, Character gender)
+  {
+    this.name = name;
+    this.age = age;
+    this.gender = gender;
+  }
+
+  public int compareTo(Person other)
+  {
+    return this.name.compareTo(other.name);
+  }
+
+  public String toString()
+  {
+    return String.format("%s (%d%c)", name, age, gender);
+  }
+
+  public String getName()
+  {
+    return name;
+  }
+
+  public Integer getAge()
+  {
+    return age;
+  }
+ 
+  public Character getGender()
+  {
+    return gender;
+  }
+}
diff --git a/usth/ICT2.2/midterm/src/Search.java b/usth/ICT2.2/midterm/src/Search.java
new file mode 100644
index 0000000..efb9e45
--- /dev/null
+++ b/usth/ICT2.2/midterm/src/Search.java
@@ -0,0 +1,57 @@
+import java.util.List;
+import java.util.Comparator;
+
+public class Search
+{
+  public static final int NOT_FOUND = -1;
+
+  public static int linear(List list, Object key)
+  {
+    for (int i = 0; i < list.size(); ++i)
+      if (key == null ? list.get(i) == null : key.equals(list.get(i)))
+        return i;
+    return NOT_FOUND;
+  }
+
+  private static <T>
+  int binary(List<? extends Comparable<? super T>> list, T key,
+             int low, int high)
+  {
+    if (high < low)
+      return NOT_FOUND;
+    var mid = (low + high) / 2;
+    var cmp = list.get(mid).compareTo(key);
+    if (cmp < 0)
+      return binary(list, key, mid + 1, high);
+    if (cmp > 0)
+      return binary(list, key, low, mid - 1);
+    return mid;
+  }
+
+  public static <T>
+  int binary(List<? extends Comparable<? super T>> list, T key)
+  {
+    return binary(list, key, 0, list.size());
+  }
+
+  private static <T>
+  int binary(List<? extends T> list, T key, Comparator<? super T> c,
+             int low, int high)
+  {
+    if (high < low)
+      return NOT_FOUND;
+    var mid = (low + high) / 2;
+    var cmp = c.compare(list.get(mid), key);
+    if (cmp < 0)
+      return binary(list, key, c, mid + 1, high);
+    if (cmp > 0)
+      return binary(list, key, c, low, mid - 1);
+    return mid;
+  }
+
+  public static <T>
+  int binary(List<? extends T> list, T key, Comparator<? super T> c)
+  {
+    return binary(list, key, c, 0, list.size());
+  }
+}
diff --git a/usth/ICT2.2/midterm/src/Sort.java b/usth/ICT2.2/midterm/src/Sort.java
new file mode 100644
index 0000000..3f146af
--- /dev/null
+++ b/usth/ICT2.2/midterm/src/Sort.java
@@ -0,0 +1,49 @@
+import java.util.List;
+import java.util.Comparator;
+
+import static java.util.Collections.swap;
+
+public class Sort
+{
+  public static <T> void selection(List<T> list, Comparator<T> comparator)
+  {
+    int i, j, m, n = list.size();
+    for (i = 0; i < n; ++i)
+      {
+        for (m = j = i; j < n; ++j)
+          if (comparator.compare(list.get(j), list.get(m)) < 0)
+            m = j;
+        swap(list, i, m);
+      }
+  }
+
+  public static <T extends Comparable<? super T>> void selection(List<T> list)
+  {
+    selection(list, new Compare<T>());
+  }
+
+  public static <T> void bubble(List<T> list, Comparator<T> comparator)
+  {
+    for (int n = list.size(), m = 0; n > 1; n = m, m = 0)
+      for (int i = 1; i < n; ++i)
+        if (comparator.compare(list.get(i), list.get(i - 1)) < 0)
+          swap(list, m = i, i - 1);
+  }
+
+  public static <T extends Comparable<? super T>> void bubble(List<T> list)
+  {
+    bubble(list, new Compare<T>());
+  }
+
+  public static <T> void heap(List<T> list, Comparator<T> comparator)
+  {
+    var heap = new Heap<T>(list, comparator);
+    for (int i = 1; i < list.size(); ++i)
+      heap.pop();
+  }
+
+  public static <T extends Comparable<? super T>> void heap(List<T> list)
+  {
+    heap(list, new Compare<T>());
+  }
+}