Leetcode: Subsets

Problem Description

Problem definition is taken from leetcode.

• Subsets

Given an integer array nums of unique elements, return all possible subsets (the power set). The solution set must not contain duplicate subsets. Return the solution in any order.

Example 1

Input: nums = [1,2,3]
Output: [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]]

Example 2

Input: nums = [0]
Output: [[],[0]]

Solution 1

Populate subsets by adding current combination to combination list at each step.

Time complexity is O(N) and space complexity is O(N).

class Solution:
    def subsets(self, nums: List[int]) -> List[List[int]]:
        subs = []
        
        self.populate(subs, nums, [], 0)
        
        return subs
        
    def populate(self, subsc, nums, comb, idx):
        subsc.append(comb)
        
        if idx==len(nums):
            return
        
        for i in range(idx, len(nums)):
            self.populate(subsc, nums, comb+[nums[i]], i+1 )