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  1. #include <iostream>
  2. #include <vector>
  3. using namespace std;
  4.  
  5. vector<vector<int> >graph;
  6. vector<bool> visited;
  7.  
  8. int max_distance, x;
  9. void DFS ( int node, int parent, int distance ){
  10.  
  11.     if ( distance > max_distance ){
  12.         max_distance = distance;
  13.         x = node;
  14.     }
  15.  
  16.     for ( auto neighbour : graph[node] ){
  17.         if ( neighbour != parent )
  18.             DFS(neighbour, node, distance + 1);
  19.     }
  20. }
  21.  
  22. int main()
  23. {
  24.     int n, m;
  25.     cin >> n >> m;
  26.     graph.resize(n);
  27.  
  28.     for ( int i = 0; i < m; i++ ){
  29.         int u, v;
  30.         cin >> u >> v;
  31.         graph[u].emplace_back(v);
  32.         graph[v].emplace_back(u);
  33.     }
  34.  
  35.     max_distance = -1;
  36.     DFS(0, -1, 0);
  37.     int y = x;
  38.     max_distance = -1;
  39.     DFS(y, -1, 0);
  40.     int z = x;
  41.  
  42.     int diameter = max_distance;
  43.     cout << diameter << endl;
  44.     return 0;
  45. }
  46.  
Success #stdin #stdout 0s 4328KB
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https://ideone.com/1d1rTy
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
secret

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