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  1. #include <iostream>
  2. #include<stack>
  3. #include<vector>
  4. #include<algorithm>
  5. #define max 100007
  6. using namespace std;
  7. int node1,Distance;
  8. void dfs(vector<int>vec[],int node,int start)
  9. {
  10. 	int dist[node+1],par[node+1],vis[node+1];
  11. 	for(int i=0;i<node+1;i++)
  12. 	dist[i]=0,par[i]=0,vis[i]=0;
  13. 	stack<int>trav;
  14. 	trav.push(start);
  15. //	for(int i=0;i<vec[1].size();i++)
  16. //	cout<<vec[1][i]<<" ";
  17. 	while(!trav.empty())
  18. 	{
  19. 		int u=trav.top();
  20. 		//cout<<u<<"  ";
  21. 		trav.pop();
  22. 		{
  23. 			if(!vis[u])
  24. 			{
  25. 				dist[u]=dist[par[u]]+1;//for storing distances from parent
  26. 				dist[start]=0;
  27. 				vis[u]++;
  28. 				for(int i=0;i<vec[u].size();i++)
  29. 				{
  30. 					int c=vec[u][i];
  31. 					trav.push(c);
  32. 					if(!vis[c])
  33. 					par[c]=u;//storing the parent
  34. 				}
  35. 			}
  36. 		}
  37.  
  38. 	}
  39. //	for(int i=1;i<node+1;i++)
  40. //	cout<<dist[i]<<" ";
  41. //	cout<<endl;
  42. 	node1=distance(dist,max_element(dist,dist+(node+1)));//finding the node with largest distance
  43. //	cout<<node1<<" ";
  44. 	Distance=dist[node1];//finding the max dist
  45. //	cout<<Distance<<" ";
  46. }
  47. int main() {
  48. 	long long int n;
  49. 	cin>>n;
  50. 	vector<int>vec[n+1];
  51. 	for(int i=0;i<n+1;i++)
  52. 	{
  53. 		int u,v;
  54. 		cin>>u>>v;
  55. 		//cout<<u<<" "<<v;
  56. 		//cout<<endl;
  57. 		vec[u].push_back(v);
  58. 		vec[v].push_back(u);
  59. 	}
  60. 	dfs(vec,n,1);
  61. 	dfs(vec,n,node1);
  62. 	cout<<Distance<<endl;
  63. 	// your code here
  64.  
  65. 	return 0;
  66. }
Success #stdin #stdout 0s 15240KB
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https://ideone.com/VgECXS
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
secret

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