Subsets [LeetCode]

Given a set of distinct integers, S, return all possible subsets.

Note:

• Elements in a subset must be in non-descending order.
• The solution set must not contain duplicate subsets.

For example,
If S = [1,2,3], a solution is:

[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

Summary: Recursive approach, we can optimize it.

     vector<vector<int> > subsets(vector<int> &S) {
         std::sort(S.begin(), S.end());
         vector<vector<int> > result;
         vector<int> subset;
         result.push_back(subset);
         if(S.size() == )
             return result;
         for(int i = ; i < S.size(); i ++) {
             vector<int> sub_s(S.begin() + i + , S.end());
             vector<vector<int> > ret = subsets(sub_s);
             for(auto item : ret){
                 item.insert(item.begin(), S[i]);
                 result.push_back(item);
             }
         }

         return result;
     }