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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	cin.tie(0);
  6. 	ios::sync_with_stdio(false);
  7.  
  8. 	int n, k;
  9. 	cin >> n >> k;
  10.  
  11. 	vector <vector <int>> g(n);
  12. 	int a, b;
  13.  
  14. 	cin >> a;
  15.  
  16. 	while (a != 0) {
  17. 		cin >> b;
  18.  
  19. 		g[a - 1].push_back(b - 1); 
  20.  
  21. 		cin >> a;
  22. 	}
  23.  
  24. 	if (g[k - 1].size() == n) {
  25. 		cout << "YES";
  26. 	} else {
  27. 		cout << "N0";
  28. 	}
  29.  
  30. 	return 0;
  31. }
Success #stdin #stdout 0s 5316KB
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stdin
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3 1
1 2
1 3
0
stdout
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N0
https://ideone.com/aslI0W
language:
C++ (gcc 8.3)
created:
5 days ago
visibility:
public

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