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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int n, m, st, en;
  5. vector<int> adj[1001];
  6. bool visited[1001];
  7. int parent[1001];
  8.  
  9. void inp(){
  10. 	cin >> n >> m;
  11. 	for(int i = 0; i < m; i++){
  12. 		int x, y; cin >> x >> y;
  13. 		adj[x].push_back(y);
  14. 		adj[y].push_back(x);
  15. 	}
  16. 	memset(visited, false, sizeof(visited));
  17. }
  18.  
  19.  
  20. bool DFS(int u){
  21. 	visited[u] = true;
  22. 	for(int v : adj[u]){
  23. 		if(!visited[v]){
  24. 			parent[v] = u;
  25. 			if(DFS(v)) return true;
  26. 		}
  27. 		else if(v != parent[u]){
  28. 			return true;
  29. 		}
  30. 	}
  31. 	return false;
  32. }
  33.  
  34. bool BFS(int u){
  35. 	visited[u] = true;
  36. 	queue<int> q;
  37. 	q.push(u);
  38. 	while(! q.empty()){
  39. 		int v = q.front(); q.pop();
  40. 		for(int x : adj[v]){
  41. 			if(!visited[x]){
  42. 				q.push(x); visited[x] = true; parent[x] = v;
  43. 			}
  44. 			else if(x != parent[v]){
  45. 				return true;
  46. 			}
  47. 		}
  48. 	}
  49. 	return false;
  50. }
  51.  
  52.  
  53. int main(){
  54. 	inp();
  55. 	for(int i = 1; i <= n; i++){
  56. 		if(!visited[i]){
  57. 			if(DFS(i)){
  58. 				cout << "YES\n";
  59. 				return 0;
  60. 			}
  61. 		}
  62. 	}
  63. 	cout << "NO\n";
  64. 	return 0;
  65. }
  66.  
Success #stdin #stdout 0.01s 5280KB
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stdin
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Standard input is empty
stdout
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NO
https://ideone.com/31aH0O
language:
C++14 (gcc 8.3)
created:
2 years ago
visibility:
public

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