1. int n, e;
  2. std::vector<int> adj[200000];
  3. std::vector<int> color; // 0 - not visited,1 = entered for visit,2 = visited
  4. std::vector<int> parent;
  5. int cycle_start, cycle_end;
  6.  
  7. bool dfs(int v){
  8.     color[v] = 1;
  9.     for(auto u : adj[v]){
  10.         if(color[u] == 0){
  11.             parent[u] = v;
  12.             if(dfs(u))return true;
  13.         }
  14.         else if(color[u] == 1){
  15.             cycle_end = v;
  16.             cycle_start = u;
  17.             return true;
  18.         }
  19.     }
  20.     color[v] = 2;
  21.     return false;
  22. }