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#include <iostream>
#include <vector>
using namespace std;

int main() {
	int n,m;
	cin>>n>>m;
	int ms[n][n]={};
	vector<int> g[n];
	for(int i=0; i<m; i++){
		int a,b;
		cin>>a>>b;
		a--; b--;
		g[a].push_back(b);
		g[b].push_back(a);
		
	}
	int x=n-1;
	string s="YES\n";
	for(int i=0; i<n; i++){
		if(g[i].size()!=x) s="NO\n";
	}
	cout<<s;
	return 0;
}
Success #stdin #stdout 0.01s 5276KB
comments (?)
stdin 
5 18
1 2
1 3
1 3
1 4
1 4
1 4
1 5
1 5
2 3
2 4
2 4
2 5
3 4
3 4
3 4
3 5
3 5
4 5
stdout 
NO
https://ideone.com/chHdsG
language:
C++ (gcc 8.3)
created:
14 days ago
visibility:
public

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