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  1. import java.util.*;
  2. import java.lang.*;
  3. import java.io.*;
  4.  
  5. class Main
  6. {
  7. 	static boolean[][] used = new boolean[101][101];
  8. 	static Scanner sc = new Scanner(System.in);
  9.  
  10. 	public static void main (String[] args) throws java.lang.Exception
  11. 	{
  12. 		int n, m;
  13. 		n = sc.nextInt();
  14. 		m = sc.nextInt();
  15. 		for(int i = 0; i < m; i++){
  16. 	     	int a, b;
  17. 	     	a = sc.nextInt();
  18. 	     	b = sc.nextInt();
  19. 	    	used[a][b] = used[b][a] = true;
  20. 	  	}
  21. 		for(int i = 1; i <= n; i++){
  22. 	    	for(int j = i+1; j <= n; j++){
  23. 	    		if(used[i][j] == false){
  24. 	    			System.out.println("NO");
  25. 	           		return;
  26. 	        	}
  27. 	    	}
  28. 	  	}
  29. 	  	System.out.println("YES");
  30. 	}
  31. }
Success #stdin #stdout 0.16s 321344KB
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stdout
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YES
https://ideone.com/OI481v
e-olymp 5077
language:
Java (HotSpot 12)
created:
8 years ago
visibility:
secret

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