【leetcode刷题】20T41-子集

示例:
输入: nums = [1,2,3]
输出:
[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

class Solution(object):
    def recursion(self, ls, nums, start, res):
        for i in range(start, len(nums)):
            tmp = copy.copy(ls)
            tmp.append(nums[i])
            res.append(tmp)
            self.recursion(tmp, nums, i + 1, res)

    def subsets(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        res = [[]]
        for i, n in enumerate(nums):
            res.append([n])
            self.recursion(ls=[n], nums=nums, start=i + 1, res=res)
        return res