78. Subsets

Solution 1: Bitwise

class Solution(object):
    def subsets(self, nums):
        N = len(nums)
        allPossibleCombinCnt = 1 << N # 2**N
        allCombin = []
        for bitMask in range(allPossibleCombinCnt): 
            currCombin = []
            for btI in range(N):
                if bitMask & (1 << btI):
                    currCombin.append(nums[btI])
            allCombin.append(currCombin)
        return allCombin

Time Complexity: O(2^N)
Space Complexity: O(1)

Solution 2: DFS

Time Complexity: O(2^N)
Space Complexity: O(2^N)

Reference

https://www.cnblogs.com/grandyang/p/4309345.html