Combination Sum II

class Solution {public:    vector<vector<int> > combinationSum2(vector<int> &num, int target) {        sort(num.begin(), num.end());        vector<vector<int> > ret;        vector<int> cur;        Helper(ret, cur, num, target, 0);        return ret;    }    void Helper(vector<vector<int> > &ret, vector<int> cur, vector<int> &num, int target, int position)    {        if(target == 0)            ret.push_back(cur);        else        {            for(int i = position; i < num.size() && num[i] <= target; i ++)            {                if(i != position && num[i] == num[i-1])                    continue;                cur.push_back(num[i]);                Helper(ret, cur, num, target-num[i], i+1);                cur.pop_back();            }        }    }};