Problems
Maximum Islands
include <bits/stdc++.h>
define ll long long int
define ld long double
using namespace std; int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
ll n, k, m;
cin>>n>>k;
m = (n*(n-1))/2;
if(k < m){
cout<<"NO";
return 0;
}
set<ll>s;
multiset<ll>ms;
for(int i = 0; i<k; i++){
ll x, y;
cin>>x>>y;
s.insert(x);
s.insert(y);
ms.insert(x);
ms.insert(y);
}
for(auto i = s.begin(); i!=s.end(); i++){
ll x = *i;
if(ms.count(x) < (n-1)){
cout<<"NO";
return 0;
}
}
cout<<"YES";
} //TECHNOBLADE NEVER DIES