组合总和 II

class Solution {
public:
    vector<vector<int>> result;
    vector<int> v;
    int sum=0;
    void back(vector<int> &candidates, int target, int k){
        if(sum==target){
            result.push_back(v);
            return;
        }
        if(sum>target){
            return;
        }
        for(int i=k;i<candidates.size();i++){
            if(i>k&&candidates[i]==candidates[i-1]) continue; 
            v.push_back(candidates[i]);
            sum+=candidates[i];
            back(candidates, target, i+1);
            v.pop_back();
            sum-=candidates[i];
        }
    }
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        sort(candidates.begin(), candidates.end());
        back(candidates, target, 0);
        return result;
    }
};