Permutations without recursive function call

Question

Requirement: Algorithm to generate all possible combinations of a set , without duplicates , or recursively calling function to return results.

The majority , if not

Answer 1

Here is an answer from @le_m. It might be of help.

The following very efficient algorithm uses Heap's method to generate all permutations of N elements with runtime complexity in O(N!):

function permute(permutation) {
  var length = permutation.length,
      result = [permutation.slice()],
      c = new Array(length).fill(0),
      i = 1, k, p;

  while (i < length) {
    if (c[i] < i) {
      k = i % 2 && c[i];
      p = permutation[i];
      permutation[i] = permutation[k];
      permutation[k] = p;
      ++c[i];
      i = 1;
      result.push(permutation.slice());
    } else {
      c[i] = 0;
      ++i;
    }
  }
  return result;
}

console.log(JSON.stringify(permute([1, 2, 3, 4])));