class Solution {
private:
    vector<int> candidates;
    vector<vector<int>> vec_vec_int;
    vector<int> vec_int;
public:
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        sort(candidates.begin(),candidates.end());
        this->candidates = candidates;
        backtrack(target, 0);
        return vec_vec_int;
    }
    void backtrack(int target, int start){
        if(target == 0){
            vec_vec_int.push_back(vec_int);
            return;
        }
        for(int i = start; i < candidates.size() && target - candidates[i] >= 0; i++){  //剪枝
            if(i > start && candidates[i] == candidates[i-1])
                continue;
            vec_int.push_back(candidates[i]);
            backtrack(target - candidates[i], i + 1);
            vec_int.pop_back();
        }
    }
};

Accepted
175/175 cases passed (8 ms)
Your runtime beats 55.79 % of cpp submissions
Your memory usage beats 94.06 % of cpp submissions (10.3 MB)