Szathmáry László honlapja @ DEIK | DLang / Lexicographically next permutation

The lexicographic permutations of [0, 1, 2] are: 012, 021, 102, 120, 201, 210.

(1) next permutation

import std.stdio;
import std.algorithm; // nextPermutation()

void main()
{
int[] a = [0, 1, 2];

do
{
writeln(a);
}
while (nextPermutation(a));

writeln("---");
a = [2, 1, 0];
writeln(nextPermutation(a)); // false
writeln(a); // [0, 1, 2]
}

Output:

[0, 1, 2]
[0, 2, 1]
[1, 0, 2]
[1, 2, 0]
[2, 0, 1]
[2, 1, 0]
---
false
[0, 1, 2]

Notes:

nextPermutation() modifies the list in-place. The list is changed to contain the lexicographically next permutation.
If the elements are in reverse order, i.e. lexicographically this is the last permutation, then it returns false; otherwise it returns true. When it returns false, it still modifies the list, so the list will contain the lexicographically first permutation.