Subset II

90. Subset II

Difficulty: Medium

Related Topics: Array, Backtracking, Bit Manipulation

Given an integer array nums that may contain duplicates, 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 = [1,2,2] Output: [[],[1],[1,2],[1,2,2],[2],[2,2]]

Example 2:

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

Code 1:

class Solution:
    def subsetsWithDup(self, nums: List[int]) -> List[List[int]]:
        res = []
        nums.sort()

        def backtrack(num, tmp):
            if num == k:
                res.append(tmp[:])
                return
            
            for i in range(num, len(nums)):
                tmp.append(nums[i])
                backtrack(i+1, tmp)
                tmp.pop()
        
        for k in range(len(nums)+1):
            backtrack(0, [])

        ans = []
        for elem in res:
            if elem not in ans:
                ans.append(elem)
        return ans

Code 2:

class Solution:
    def subsetsWithDup(self, nums: List[int]) -> List[List[int]]:
        res = []
        nums.sort()

        def backtrack(ind, tmp):
            if ind == len(nums):
                res.append(tmp[:])
                return
            
            # All subsets that include nums[ind]
            tmp.append(nums[ind])
            backtrack(ind + 1, tmp)
            tmp.pop()
            # All subsets that don't include nums[ind]
            while ind + 1 < len(nums) and nums[ind] == nums[ind+1]:
                ind += 1
            backtrack(ind + 1, tmp)
        
        backtrack(0, [])
        return res