Given a set of distinct integers, nums, return all possible subsets.

Note: The solution set must not contain duplicate subsets.


For example,
If nums = [1,2,3], a solution is:



[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

class Solution(object):
    def subsets(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        def dfs(nums, index, path, ans):
            ans.append(path)
            [dfs(nums, i + 1, path + [nums[i]], ans) for i in xrange(index, len(nums))]
        ans = []
        dfs(nums, 0, [], ans)
        return ans