Add /r/dailyprogrammer Challenge #305

1 files changed, 54 insertions, 0 deletions

diff --git a/daily/305hard/number.pas b/daily/305hard/number.pas
new file mode 100644
index 0000000..6a2d6e5
--- /dev/null
+++ b/daily/305hard/number.pas
@@ -0,0 +1,54 @@
+var
+  a: array[0..15] of byte;
+
+
+function factorial(n: byte): int64;
+  begin
+    if n < 2 then
+      exit(1);
+    factorial := factorial(pred(n)) * n
+  end;
+
+
+function number(
+  a: array of byte;
+  depth: byte
+): int64;
+
+  var
+    i, sum: byte;
+    b: array[0..9] of byte;
+
+  begin
+    if depth = 15 then
+      begin
+        sum := 0;
+        for i := 1 to 15 do
+          inc(sum, a[i]);
+        if sum <> 69 then
+          exit(0);
+        number := 1307674368000; (* factorial(15) *)
+        for i := 0 to 9 do
+          b[i] := 0;
+        for i := 1 to 15 do
+          inc(b[a[i]]);
+        for i := 0 to 9 do
+          number := number div factorial(b[i]);
+        exit
+      end;
+
+    number := 0;
+    i := a[depth];
+    inc(depth);
+    repeat
+      a[depth] := i;
+      number := number + number(a, depth);
+      inc(i)
+    until i = 10
+  end;
+
+
+begin
+  a[0] := 0;
+  writeln(number(a, 0))
+end.