7 files changed, 179 insertions, 0 deletions
diff --git a/usth/MATH2.3/4/README.md b/usth/MATH2.3/4/README.md
new file mode 100644
index 0000000..880dacf
--- /dev/null
+++ b/usth/MATH2.3/4/README.md
@@ -0,0 +1,71 @@
+# Booleans
+## Problem 1
+`deg3.c` prints the a table listing the set of values of all 256 Boolean
+functions of degree three to stdout.
+
+## Problem 2
+`sum-of-products.c` takes 2 natural numbers `n` and `f` from stdin, where `f`
+is the encoded truth table of a Boolean function of degree `n`, for example,
+
+|   x0  |   x1  | value |
+| :---: | :---: | :---: |
+|   0   |   0   |   1   |
+|   0   |   1   |   0   |
+|   1   |   0   |   1   |
+|   1   |   1   |   0   |
+
+will be encoded as `0b0101 = 5`.  The program then print the bitwise arithmetic
+sum-of-products expression to stdout, e.g.
+
+### Input
+    2 5
+
+### Output
+    ~x0&~x1 | ~x0&x1
+
+## Problem 3
+`k-map`, e.g.
+
+### Input
+    0 0 0 1
+    0 0 1 0
+    0 1 0 1
+    1 0 0 0
+    1 1 1 0
+    0 1 1 0
+    1 1 0 1
+    1 0 1 0
+
+### Output
+       00  01  10  11
+    0   1   0   1   1
+    0   0   0   0   0
+
+## Problem 4
+`threshold.c` takes in natural number `n`, a real threshold value `t` and `n`
+weights, then `n` boolean values from stdin and print to stdout the output of
+the given threshold gate, e.g.
+
+### Input
+    7 0.25051534245890184
+    0.11609819805105248
+    0.7924365005827357
+    0.9835187780201641
+    0.4235209817923591
+    0.08303890030044114
+    0.7196176517110272
+    0.988645113198539
+    1 1 0 1 1 0 1
+
+### Output
+    1
+
+## Problem 5
+`sum.c` takes similar input format from stdin and print the bitwise arithmetic
+expression using only bit flip (`~`) and addition (`|`) to stdout, e.g.
+
+### Input
+    3 69
+
+### Output
+    ~(~x0 | x1 | x2) | ~(~x0 | ~x1 | x2) | ~(~x0 | ~x1 | ~x2)
diff --git a/usth/MATH2.3/4/[Ch_Boolean]_Practical.pdf b/usth/MATH2.3/4/[Ch_Boolean]_Practical.pdf
new file mode 100644
index 0000000..fd3680e
--- /dev/null
+++ b/usth/MATH2.3/4/[Ch_Boolean]_Practical.pdf
Binary files differdiff --git a/usth/MATH2.3/4/deg3.c b/usth/MATH2.3/4/deg3.c
new file mode 100644
index 0000000..a4f5726
--- /dev/null
+++ b/usth/MATH2.3/4/deg3.c
@@ -0,0 +1,18 @@
+#include <stdio.h>
+
+int main()
+{
+	printf("(x y z)");
+	for (int i = 0; i < 8; ++i)
+		printf("\t(%d %d %d)", i & 4 && 1, i & 2 && 1, i & 1 && 1);
+	putchar(10);
+
+	for (int i = 0; i < 256; ++i) {
+		printf("f%02x", i);
+		for (int j = 0; j < 8; ++j)
+			printf("\t%d", i & 1 << j && 1);
+		putchar(10);
+	}
+
+	return 0;
+}
diff --git a/usth/MATH2.3/4/k-map.c b/usth/MATH2.3/4/k-map.c
new file mode 100644
index 0000000..ef19b80
--- /dev/null
+++ b/usth/MATH2.3/4/k-map.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+int main()
+{
+	int x, y, z, f[8];
+
+	for (int i = 0; i < 8; ++i) {
+		scanf("%d %d %d", &x, &y, &z);
+		scanf("%d", f + x + (y << 1) + (z << 2));
+	}
+
+	printf("\t00\t01\t10\t11\n0\t%d\t%d\t%d\t%d\n0\t%d\t%d\t%d\t%d\n",
+	       f[0], f[1], f[2], f[3], f[4], f[5], f[6], f[7]);
+
+	return 0;
+}
diff --git a/usth/MATH2.3/4/sum-of-products.c b/usth/MATH2.3/4/sum-of-products.c
new file mode 100644
index 0000000..3fac72b
--- /dev/null
+++ b/usth/MATH2.3/4/sum-of-products.c
@@ -0,0 +1,25 @@
+#include <stdio.h>
+
+int main()
+{
+	size_t n, f;
+	int b = 0;
+
+	scanf("%zu %zu", &n, &f);
+	for (size_t i = 0; !(i >> n); ++i) {
+		if (!(f & 1 << i))
+			continue;
+		if (b)
+			printf(" | ");
+		b = 1;
+		printf(i & 1 ? "x0" : "~x0");
+		for (size_t j = 1; j < n; ++j)
+			if (i & 1 << j)
+				printf("&x%zu", j);
+			else
+				printf("&~x%zu", j);
+	}
+	putchar(10);
+
+	return 0;
+}
diff --git a/usth/MATH2.3/4/sum.c b/usth/MATH2.3/4/sum.c
new file mode 100644
index 0000000..8fd28f3
--- /dev/null
+++ b/usth/MATH2.3/4/sum.c
@@ -0,0 +1,26 @@
+#include <stdio.h>
+
+int main()
+{
+	size_t n, f;
+	int b = 0;
+
+	scanf("%zu %zu", &n, &f);
+	for (size_t i = 0; !(i >> n); ++i) {
+		if (!(f & 1 << i))
+			continue;
+		if (b)
+			printf(" | ");
+		b = 1;
+		printf(i & 1 ? "~(x0" : "~(~x0");
+		for (size_t j = 1; j < n; ++j)
+			if (i & 1 << j)
+				printf(" | ~x%zu", j);
+			else
+				printf(" | x%zu", j);
+		putchar(41);
+	}
+	putchar(10);
+
+	return 0;
+}
diff --git a/usth/MATH2.3/4/threshold.c b/usth/MATH2.3/4/threshold.c
new file mode 100644
index 0000000..5c39b3c
--- /dev/null
+++ b/usth/MATH2.3/4/threshold.c
@@ -0,0 +1,23 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main()
+{
+	size_t n;
+	scanf("%zu", &n);
+
+	double t, *weights = malloc(n * sizeof(double));
+	scanf("%lf", &t);
+	for (size_t i = 0; i < n; ++i)
+		scanf("%lf", weights + i);
+
+	int tmp;
+	for (size_t i = 0; i < n; ++i) {
+		scanf("%d", &tmp);
+		t -= tmp && weights[i];
+	}
+
+	putchar((t <= 0) + 48);
+	putchar(10);
+	return 0;
+}