Leetcode: 90. Subsets II

Description

Given a collection of integers that might contain duplicates, nums, return all possible subsets.

Note: The solution set must not contain duplicate subsets.

Example

If nums = [1,2,2], a solution is:

[
    [2],
    [1],
    [1,2,2],
    [2,2],
    [1,2],
    []
]

思路

• 回溯，而後注意去重問題

代碼

class Solution {
public:
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        vector<vector<int>> res;
        sort(nums.begin(), nums.end());
        
        vector<int> vec;
        subsetWithDupBacktrack(res, vec, nums, 0);
        
        return res;
    }
    
    void subsetWithDupBacktrack(vector<vector<int>>& res, vector<int>& vec, 
        vector<int>& nums, int t){
            res.push_back(vec);
            
            for(int i = t; i < nums.size(); ++i){
                if(i == t || nums[i] != nums[i - 1]){
                    vec.push_back(nums[i]);
                    
                    subsetWithDupBacktrack(res, vec, nums, i + 1);
                    
                    vec.pop_back();
                }
            }
        }
};