Permutations

Given a collection of numbers, return all possible permutations.
For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].


Solution :
This is done recursively by making permutations resulting from swapping of two elements. The below diagram can make it clear.

We start with k=0 and swap the element at ith index with element at kth index.

At the first level for k = 0, we swap num[k] with num[i] where i varies from k to number of elements in the array. We do this at all levels where value of k increases till it is equal to the number of elements in the array.

Here is the program for it :

Please comment to add something.