[leetcode]Subsets

枚举每个元素,取还是不取

class Solution {
public:
    void dfs(vector<vector<int> >& ans , vector<int>& s , vector<int>& tmp , int n , int dep) {
      ans.push_back(tmp);
      
      for(int i = dep ; i < n ; ++i) {
          tmp.push_back(s[i]);
          dfs(ans , s, tmp , n , i+1);
          tmp.pop_back();
      }
       
    }
    vector<vector<int> > subsets(vector<int> &S) {
        vector<vector<int> >ans;
        if(S.size() < 0) return ans;
        vector<int> tmp;
        sort(S.begin() , S.end());
        dfs(ans , S , tmp , S.size() , 0);
        return ans;
    }
};