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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. void dfs (int v, vector <vector <int>>& g, vector<bool>& visited, int& res) {
  5. 	visited[v] = true; res++;
  6.  
  7. 	for (int i : g[v]) {
  8. 		if (!visited[i]) {
  9. 			dfs(i, g, visited, res);
  10. 		}
  11. 	}
  12. }
  13.  
  14. int main() {
  15. 	cin.tie(0);
  16. 	ios::sync_with_stdio(false);
  17.  
  18. 	int n, k;
  19. 	cin >> n >> k;
  20.  
  21. 	vector <vector <int>> g(n);
  22. 	vector <bool> visited(n, false);
  23.  
  24.  
  25. 	int a, b;
  26. 	cin >> a;
  27.  
  28. 	while (a != 0) {
  29. 		cin >> b;
  30.  
  31. 		g[a - 1].push_back(b - 1);
  32.  
  33. 		cin >> a;
  34.  
  35. 	}
  36.  
  37.  
  38.  
  39. 	int res = 0;
  40.  
  41. 	// for (int i = 0; i < n; i++) {cout << i << ": "; for (int q : g[i]) {cout << q;}cout<<"\n";}
  42.  
  43. 	dfs(k - 1, g, visited, res);
  44.  
  45. 	if (res == n) {
  46. 		cout << "Yes";
  47. 	} else {
  48. 		cout << "No";
  49. 	}
  50. 	return 0;
  51. }
Success #stdin #stdout 0s 5308KB
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https://ideone.com/z6OwMR
language:
C++ (gcc 8.3)
created:
5 days ago
visibility:
public

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