1 class Solution { 2 public: 3     void dfs(vector<int> v,int i,vector<vector<int> > &ans,vector<int> vv,int k){ 4         if(vv.size()==k){ 5             ans.push_back(vv); 6             return; 7         } 8         for(int j=i+1;j<v.size();j++){ 9             if(j!=i+1&&v[j]==v[j-1]) continue;10             vv.push_back(v[j]);11             dfs(v,j,ans,vv,k);12             vv.pop_back();13         }14     }15     vector<vector<int> > combine(int n, int k) {16         vector<int> v(n);17         for(int i=0;i<n;i++) v[i]=i+1;18         vector<vector<int> > ans;19         vector<int> vv;20         for(int i=0;i<v.size();i++){21             vv.push_back(v[i]);22             dfs(v,i,ans,vv,k);23             vv.pop_back();24         }25         return ans;26     }27 };