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. std::vector<bool> visited;
  6. int cycle_start, cycle_end;
  7.  
  8. bool dfs(int v, int par){
  9.     visited[v] = 1;
  10.     for(auto u : adj[v]){
  11.         if(u == par)continue;
  12.         if(visited[u] == 1){
  13.             cycle_end =  v;
  14.             cycle_start = u;
  15.             return true;
  16.         }
  17.         parent[u] = v;
  18.         if(dfs(u, parent[u])){
  19.             return true;
  20.         }
  21.     }
  22.     return false;
  23. }