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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. int main() {
  5. 	ios::sync_with_stdio(false);
  6. 	cin.tie(nullptr);
  7.  
  8.  
  9. 	int n, m;
  10. 	cin >> n >> m;
  11. 	if (n == 1) {
  12. 		cout << "NO\n";
  13. 		exit(0);
  14. 	}
  15. 	cout << "YES\n";
  16. 	unordered_set<string> st;
  17. 	st.reserve(m * 2);
  18.  
  19. 	auto frmat = [](int a, int b) {
  20. 		return to_string(min(a, b)) + "-" + to_string(max(a, b));
  21. 	};
  22.  
  23. 	for (int i = 0; i < m; i++) {
  24. 		int a, b;
  25. 		cin >> a >> b;
  26. 		st.insert(frmat(a, b));
  27. 	}
  28.  
  29. 	int half = n / 2;
  30. 	for (int i = 1; i <= half; i++) {
  31. 		for (int j = i + 1; j <= half; j++) {
  32. 			string edge = frmat(i, j);
  33. 			if (!st.count(edge)) {
  34. 				cout << i << ' ' << j << '\n';
  35. 			}
  36. 		}
  37. 	}
  38. 	for (int i = half + 1; i <= n; i++) {
  39. 		for (int j = i + 1; j <= n; j++) {
  40. 			string edge = frmat(i, j);
  41. 			if (!st.count(edge)) {
  42. 				cout << i << ' ' << j << '\n';
  43. 			}
  44. 		}
  45. 	}
  46.  
  47. 	return 0;
  48. }
Success #stdin #stdout 0.01s 5308KB
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stdin
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Standard input is empty
stdout
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YES
https://ideone.com/jR8VAG
language:
C++14 (gcc 8.3)
created:
4 days ago
visibility:
public

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