1 files changed, 98 insertions, 0 deletions
diff --git a/daily/287easy/kaprekar.pas b/daily/287easy/kaprekar.pas
new file mode 100644
index 0000000..7378f2d
--- /dev/null
+++ b/daily/287easy/kaprekar.pas
@@ -0,0 +1,98 @@
+type
+  aos = array[0 .. 3] of shortint;
+
+function largest_digit(n: smallint): shortint;
+  var
+    m: shortint;
+
+  begin
+    m := n div 1000;
+
+    if m < n mod 1000 div 100 then
+      m := n mod 1000 div 100;
+
+    if m < n mod 100 div 10 then
+      m := n mod 100 div 10;
+
+    if m < n mod 10 then
+      exit(n mod 10)
+    else
+      exit(m)
+  end;
+
+function sorted_digits(n: smallint): aos;
+  var
+    a: aos;
+    i, j: shortint;
+
+  begin
+    a[0] := n div 1000;
+    a[1] := n mod 1000 div 100;
+    a[2] := n mod 100 div 10;
+    a[3] := n mod 10;
+
+    for i := 0 to 2 do
+      for j := i + 1 to 3 do
+        if a[i] < a[j] then
+          begin
+            inc(a[i], a[j]);
+            a[j] := a[i] - a[j];
+            dec(a[i], a[j])
+          end;
+
+    exit(a)
+  end;
+
+function desc_digits(n: smallint): smallint;
+  var
+    a: aos;
+
+  begin
+    a := sorted_digits(n);
+
+    exit(a[0] * 1000 + a[1] * 100 + a[2] * 10 + a[3])
+  end;
+
+function asc_digits(n: smallint): smallint;
+  var
+    a: aos;
+
+  begin
+    a := sorted_digits(n);
+
+    exit(a[3] * 1000 + a[2] * 100 + a[1] * 10 + a[0])
+  end;
+
+function kaprekar(n: smallint): qword;
+  var
+    i: shortint = 0;
+
+  begin
+    while n <> 6174 do
+      begin
+        n := desc_digits(n) - asc_digits(n);
+        inc(i)
+      end;
+
+    exit(i)
+  end;
+
+begin
+  writeln('largest_digit(1234) -> ', largest_digit(1234));
+  writeln('largest_digit(3253) -> ', largest_digit(3253));
+  writeln('largest_digit(9800) -> ', largest_digit(9800));
+  writeln('largest_digit(3333) -> ', largest_digit(3333));
+  writeln('largest_digit(120) -> ', largest_digit(120));
+  writeln;
+
+  writeln('desc_digits(1234) -> ', desc_digits(1234));
+  writeln('desc_digits(3253) -> ', desc_digits(3253));
+  writeln('desc_digits(9800) -> ', desc_digits(9800));
+  writeln('desc_digits(3333) -> ', desc_digits(3333));
+  writeln('desc_digits(120) -> ', desc_digits(120));
+  writeln;
+
+  writeln('kaprekar(6589) -> ', kaprekar(6589));
+  writeln('kaprekar(5455) -> ', kaprekar(5455));
+  writeln('kaprekar(6174) -> ', kaprekar(6174))
+end.