Leetcode#78 Subsets

 1 vector<vector<int> > res;
 2 
 3 void dfs(vector<int> &S, vector<int> ans, int pos) {
 4   if (pos == S.size()) {
 5     res.push_back(ans);
 6     return;
 7   }
 8   dfs(S, ans, pos + 1);
 9   ans.push_back(S[pos]);
10   dfs(S, ans, pos + 1);
11 }
12 
13 vector<vector<int> > subsets(vector<int> &S) {
14   sort(S.begin(), S.end());
15   dfs(S, vector<int>(), 0);
16   return res;
17 }