Lang:G++
Edit12345678910111213141516171819202122232425262728293031#include<cstdio>#include<cstdlib>#include<cstring>#include<stdlib.h>#include<iostream>#include<map>#include<set>using namespace std;typedef pair<int,int> P;set<P> sk;int main(){int T;cin>>T;while(T--){sk.clear();int n,m;cin>>n>>m;for(int i=0;i<m;i++){int u,v;cin>>u>>v;sk.insert(P(u,v));sk.insert(P(v,u));}printf((int)sk.size()==2*n-2?"YES\n":"NO\n");}return 0;