vector<vector<int>> create_map(int N, int M, vector<int> A, vector<int> B) { int K = 2*N; // safe for DFS Euler tour vector<vector<int>> ans(K, vector<int>(K)); vector<vector<int>> adj(N+1); vector<int> tour; for (int i = 0; i < M; i++){ adj[A[i]].push_back(B[i]); adj[B[i]].push_back(A[i]); } function<void(int,int)> dfs = [&](int x, int p){ tour.push_back(x); for (int h : adj[x]){ if (h == p) continue; dfs(h, x); tour.push_back(x); } }; dfs(1, 0); int L = tour.size(); for (int i = 0; i < K; i++){ for (int j = 0; j < K; j++){ ans[i][j] = tour[j % L]; } } return ans; }

worldmap.cpp:1:1: error: 'vector' does not name a type
    1 | vector<vector<int>> create_map(int N, int M, vector<int> A, vector<int> B) {
      | ^~~~~~