leetcode:Subsets

class Solution {public:    vector<vector<int> > subsets(vector<int> &S) {        vector<vector<int>> res;        vector<int> list;        if(S.size()==0)        {            res.push_back(list);        }        else        {            int head = S[0];            S.erase(S.begin());            vector<vector<int>>res_temp = subsets(S);            for(int i=0;i<res_temp.size();i++)            {                list = res_temp[i];                res.push_back(list);                list.push_back(head);                sort(list.begin(),list.end());                res.push_back(list);            }        }        return res; }};