Combinations sum

class Solution {
public:

    void f(vector<int>& candidates,vector<vector<int>> &ans,vector<int>&cur,int i, int n, int target){

        if(target==0){
            ans.push_back(cur);
            return;
        }

        if(i==n || target<0)return;

        cur.push_back(candidates[i]);
        f(candidates,ans,cur,i,n,target-candidates[i]);

        cur.pop_back();

        f(candidates,ans,cur,i+1,n,target);


    }

    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {

        vector<vector<int>> ans;
        vector<int>cur;
        int i = 0;
        int n =candidates.size();

        f(candidates,ans,cur,i,n,target);

        return ans;

    }
};