Permutation of array

Question

For example I have this array:

int a[] = new int[]{3,4,6,2,1};

I need list of all permutations such that if one is like this, {3,2,1

Answer 1

Visual representation of the 3-item recursive solution: http://www.docdroid.net/ea0s/generatepermutations.pdf.html

Breakdown:

1. For a two-item array, there are two permutations:
   • The original array, and
   • The two elements swapped
2. For a three-item array, there are six permutations:
   • The permutations of the bottom two elements, then
   • Swap 1st and 2nd items, and the permutations of the bottom two element
   • Swap 1st and 3rd items, and the permutations of the bottom two elements.
   • Essentially, each of the items gets its chance at the first slot