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Function std.algorithm.sorting.nextPermutation

Permutes range in-place to the next lexicographically greater permutation.

bool nextPermutation(alias less, BidirectionalRange) (
  BidirectionalRange range
if (isBidirectionalRange!BidirectionalRange && hasSwappableElements!BidirectionalRange);

The predicate less defines the lexicographical ordering to be used on the range.

If the range is currently the lexicographically greatest permutation, it is permuted back to the least permutation and false is returned. Otherwise, true is returned. One can thus generate all permutations of a range by sorting it according to less, which produces the lexicographically least permutation, and then calling nextPermutation until it returns false. This is guaranteed to generate all distinct permutations of the range exactly once. If there are N elements in the range and all of them are unique, then N! permutations will be generated. Otherwise, if there are some duplicated elements, fewer permutations will be produced.

// Enumerate all permutations
int[] a = [1,2,3,4,5];
    // use the current permutation and
    // proceed to the next permutation of the array.
} while (nextPermutation(a));


less The ordering to be used to determine lexicographical ordering of the permutations.
range The range to permute.


false if the range was lexicographically the greatest, in which case the range is reversed back to the lexicographically smallest permutation; otherwise returns true.

See Also



// Step through all permutations of a sorted array in lexicographic order
int[] a = [1,2,3];
writeln(nextPermutation(a)); // true
writeln(a); // [1, 3, 2]
writeln(nextPermutation(a)); // true
writeln(a); // [2, 1, 3]
writeln(nextPermutation(a)); // true
writeln(a); // [2, 3, 1]
writeln(nextPermutation(a)); // true
writeln(a); // [3, 1, 2]
writeln(nextPermutation(a)); // true
writeln(a); // [3, 2, 1]
writeln(nextPermutation(a)); // false
writeln(a); // [1, 2, 3]


// Step through permutations of an array containing duplicate elements:
int[] a = [1,1,2];
writeln(nextPermutation(a)); // true
writeln(a); // [1, 2, 1]
writeln(nextPermutation(a)); // true
writeln(a); // [2, 1, 1]
writeln(nextPermutation(a)); // false
writeln(a); // [1, 1, 2]


Andrei Alexandrescu


Boost License 1.0.