problem86.cpp

#include <bits/stdc++.h>
using namespace std;

class CastlelandExplorer {
  int n;  // Number of castles
  vector<vector<int>> adj; // Adjacency list
  vector<bool> visited; // Visited flag
  vector<int> order; // DFS order

public:
  void readInput() {
    cin >> n;
    adj.resize(n);
    visited.assign(n, false);
    cin.ignore(); // clear newline

    for (int i = 0; i < n; ++i) {
      string line;
      getline(cin, line);
      istringstream iss(line);
      int v;
      while (iss >> v) {
        adj[i].push_back(v);
      }
    }
  }

  void dfs(int u) {
    visited[u] = true;
    order.push_back(u);

    for (int v : adj[u]) {
      if (!visited[v]) {
        dfs(v);
      }
    }
  }

  void display() {
    dfs(0); // Start from castle 0
    for (int i = 0; i < order.size(); ++i) {
      if (i) cout << " ";
      cout << order[i];
    }
    cout << endl;
  }
};

int main() {
  CastlelandExplorer explorer;
  explorer.readInput();
  explorer.display();
  return 0;
}