78. 子集

78. 子集
class Solution:
    def subsets(self, nums: List[int]) -> List[List[int]]:
        res = []
        path = []
        n = len(nums)
        def backtracking(nums, startIndex):
            res.append(path[:])
            for i in range(startIndex,len(nums)):
                path.append(nums[i])
                backtracking(nums,i+1)
                path.pop()#回溯
        backtracking(nums,0)
        return res