Permutations

Given a collection of distinct 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],
  [3,2,1]
]

Take any number as the first number and append any permutation of the other numbers.

class Solution(object):
    def permute(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        return [[n] + p
                for i,n in enumerate(nums)
                for p in self.permute(nums[:i] + nums[i+1:])
            ] or [[]]