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Subsets II⚓︎

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Description⚓︎

Given an integer array nums that may contain duplicates, return all possible subsets (the power set).

A subset of an array is a selection of elements (possibly none) of the array.

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] <= 10

Solution⚓︎

Way 1⚓︎

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class Solution {
private:
    vector<vector<int>> res;
    vector<int> path;
    void backtracking(vector<int>& nums, int startIndex) {
        res.push_back(path);
        unordered_set<int> used;
        for (int i = startIndex; i < nums.size(); i++) {
            if (used.find(nums[i]) != used.end()) continue;
            used.insert(nums[i]);
            path.push_back(nums[i]);
            backtracking(nums, i + 1);
            path.pop_back();
        }
    }
public:
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        backtracking(nums, 0);
        return res;
    }
};

Way 2⚓︎

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class Solution {
private:
    vector<vector<int>> res;
    vector<int> path;
    void backtracking(vector<int> &nums, int startIndex) {
        res.push_back(path);
        for (int i = startIndex; i < nums.size(); i++) {
            if (i > startIndex && nums[i] == nums[i - 1]) continue;
            path.push_back(nums[i]);
            backtracking(nums, i + 1);
            path.pop_back();
        }
    }
public:
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
       sort(nums.begin(), nums.end());
       backtracking(nums, 0);
       return res; 
    }
};