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  1. #include <iostream>
  2. #include <vector>
  3. #include <map>
  4. using namespace std;
  5.  
  6. vector<int> Map[200001];
  7. int dist[200001];
  8.  
  9. void dfs(int node,int parent)
  10. {
  11. 	for(int i=0;i<Map[node].size();i++)
  12. 	{
  13. 		if(parent != Map[node][i])
  14. 		{
  15. 			dist[Map[node][i]] = 1+dist[node];
  16. 			dfs(Map[node][i],node);
  17. 		}
  18. 	}
  19. }
  20.  
  21.  
  22. int main() {
  23.  
  24. 	int n;
  25. 	cin>>n;
  26.  
  27. 	for(int i=0;i<n-1;i++)
  28. 	{
  29. 		int a,b;
  30. 		cin>>a>>b;
  31.  
  32. 		Map[a-1].push_back(b-1);
  33. 		Map[b-1].push_back(a-1);
  34. 	}
  35.  
  36. 	dist[0]=0;
  37. 	dfs(0,-1);
  38.  
  39. 	int maxDist =0;
  40. 	int node=0;
  41. 	for(int i=0;i<n;i++)
  42. 	{
  43. 		if(dist[i] > maxDist)
  44. 		{
  45. 			maxDist = dist[i];
  46. 			node=i;
  47. 		}
  48. 	}
  49.  
  50. 	for(int i=0;i<n;i++)
  51. 	{
  52. 		dist[i]=0;
  53. 	}
  54. 	dfs(node,-1);
  55.  
  56. 	maxDist=0;
  57. 	for(int i=0;i<n;i++)
  58. 	{
  59. 		maxDist = max(maxDist,dist[i]);
  60. 	}
  61.  
  62. 	cout<<maxDist<<endl;
  63.  
  64. 	return 0;
  65. }
Success #stdin #stdout 0.01s 8252KB
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https://ideone.com/fWoCpe
language:
C++14 (gcc 8.3)
created:
11 days ago
visibility:
public

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