Hi, here's your problem today. This problem was recently asked by Facebook:

You are given an array of integers. Return all the permutations of this array.

<pre lang=py>
def permute(nums):
  # Fill this in.

print permute([1, 2, 3])
# [[1, 2, 3], [2, 1, 3], [2, 3, 1], [1, 3, 2], [3, 1, 2], [3, 2, 1]]
</pre>