78. Subsets

class Solution:
    def subsets(self, nums: List[int]) -> List[List[int]]:
        L = len(nums)
        ans = [[]]

        def recurse(index, arr):
            nonlocal ans
            if index < L:
                recurse(index + 1, arr + [nums[index]])
                recurse(index + 1, arr)            
            else:
                ans.append(arr)

        for index, e in enumerate(nums):
            recurse(index + 1, [e])

        return ans