LeetCode - Combinations Sum

class Solution {
public:
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        sort(candidates.begin(), candidates.end());
        vector<vector<int>> res;
        vector<int> out;
        helper(candidates, out, 0, target, res);
        return res;
    }
    void helper(vector<int>& candidates, vector<int>& out, int pos, int target, vector<vector<int>>& res){
        if(target==0) res.push_back(out);
        if(target<0) return;
        for(int i=pos;i<candidates.size();i++){
            out.push_back(candidates[i]);
            helper(candidates, out, i, target-candidates[i], res);
            out.pop_back();
        }
    }
};