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;
 }
};