90. Subsets II

Medium

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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]]

Constraints:

• 1 <= nums.length <= 10

• -10 <= nums[i] <= 1

class Solution:
    def subsetsWithDup(self, nums: List[int]) -> List[List[int]]:
        nums.sort()
        def recursion(nums, start, path, result):
            result.append(path[:])
            for index in range(start, len(nums)):
                # Eliminate the dup with sort and then the condition: do not put this element inside, if it has same element before && the former dup has not been put into it. 
                if index != start and nums[index] == nums[index-1]:
                    continue
                path.append(nums[index])
                # print(path)
                recursion(nums, index+1, path, result)
                path.pop()
        result = []
        recursion(nums, 0, [], result)
        return result