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  1. #include<stdio.h>
  2. #include<string.h>
  3. int main(){
  4. 	int n,m,i,v1,v2;
  5. 	scanf("%d %d",&n,&m);
  6. 	if(m!=n-1) return printf("NO"),0;
  7. 	else{
  8. 		if(n==1) return printf("YES"),0;
  9. 		int arr[n];
  10. 		memset(arr,0,n*sizeof(int));
  11. 		for(i=0;i<m;i++){
  12. 			scanf("%d %d",&v1,&v2);
  13. 			arr[v1-1]++;
  14. 			arr[v2-1]++;
  15. 		}
  16. 		for(i=0;i<n;i++)
  17. 			if(arr[i]==0) return printf("NO"),0;
  18. 		if(i==n) return printf("YES"),0;
  19. 	}
  20. }
  21.  
Success #stdin #stdout 0s 2172KB
comments (?)
stdin
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3 2
1 2 
1 3
stdout
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YES
https://ideone.com/1OE5vE
language:
C (clang 8.0)
created:
7 years ago
visibility:
public

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