Many Cycles

#include <bits/stdc++.h>
using namespace std;
int t;
int n, m;

vector<int> rt[101];

int u[101];
int f(int c, int p){
  if (u[c]){
    ++u[c];
    return 1;
  }
  u[c]=1;
  int cc=0;
  for (auto w:rt[c]){
    if (w==p) continue;
    int a=f(w, c);
    if (a==-1) return -1;
    cc+=a;
  }
  if (cc>2) return -1;
  cc-=2*(u[c]-1);
  return cc;
}

int main(){
  ios_base::sync_with_stdio(0);cin.tie(0);
  cin >> t;
  for (int ii=0;ii<t;++ii){
    cin >> n >> m;
    for (int i=1;i<=n;++i) rt[i].clear();
    for (int i=1;i<=n;++i) u[i]=0;
    for (int i=0;i<m;++i){
      int a, b;
      cin >> a >> b;
      rt[a].push_back(b);
      rt[b].push_back(a);
    }
    bool h=0;
    for (int i=1;i<=n;++i){
      if (!u[i]) {
        int w=f(i,i);
        if (w==-1) h=1;
      }
    }
    cout << (h?"YES\n":"NO\n");
  }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED