Data commit

Task/Combinations-and-permutations/D/combinations-and-permutations.d

@@ -0,0 +1,26 @@
+import std.stdio, std.mathspecial, std.range, std.algorithm,
+       std.bigint, std.conv;
+
+enum permutation = (in uint n, in uint k) pure =>
+    reduce!q{a * b}(1.BigInt, iota(n - k + 1, n + 1));
+
+enum combination = (in uint n, in uint k) pure =>
+    n.permutation(k) / reduce!q{a * b}(1.BigInt, iota(1, k + 1));
+
+enum bigPermutation = (in uint n, in uint k) =>
+    exp(logGamma(n + 1) - logGamma(n - k + 1));
+
+enum bigCombination = (in uint n, in uint k) =>
+    exp(logGamma(n + 1) - logGamma(n - k + 1) - logGamma(k + 1));
+
+void main() {
+    12.permutation(9).writeln;
+    12.bigPermutation(9).writeln;
+    60.combination(53).writeln;
+    145.bigPermutation(133).writeln;
+    900.bigCombination(450).writeln;
+    1_000.bigCombination(969).writeln;
+    15_000.bigPermutation(73).writeln;
+    15_000.bigPermutation(1185).writeln;
+    writefln("%(%s\\\n%)", 15_000.permutation(74).text.chunks(50));
+}