Permutations(improve)

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].

I can not think of how to solve this problem in a elegant way. I know it needs to be done recursively, while... it will for sure takes me a lot of time to consider. Anyway, this is really a good piece of code!