NC27 集合的所有子集(一)

class Solution {
public:
    vector<vector<int>>ans;
   
    void dfs(vector<int> &S,vector<int>&v,int index){
        ans.push_back(v);
        for(int i=index;i<S.size();i++){
            v.push_back(S[i]);
            dfs(S,v,i+1);
            v.pop_back();
        }
    }
    vector<vector<int> > subsets(vector<int> &S) {
        vector<int>v;
        dfs(S,v,0);
        return ans;
    }
};