Submission #65435317

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Source Code Expand

// Problem: 'C - Cycle Graph?'
// Contest: 'AtCoder - AtCoder Beginner Contest 404'
// URL: 'https://atcoder.jp/contests/abc404/tasks/abc404_c'
// Memory Limit: 1024 MB
// Time Limit: 2000 ms
//
// Powered by competitive-companion.el (https://github.com/luishgh/competitive-companion.el)

#include <bits/stdc++.h>

using namespace std;

#define _ ios_base::sync_with_stdio(0);cin.tie(0);
#define endl '\n'

typedef long long ll;

const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3fll;

const int MAX = 2e5 + 10;

vector<int> g[MAX];
int d[MAX];
int v[MAX];

int main() {_;

  int n, m; cin >> n >> m;

  for (int i = 0; i < n; i++) d[i] = 0, v[i] = 0;

  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);
  }

  if (m != n) {
    cout << "No" << endl;
    exit(0);
  }

  queue<int> q;
  q.push(0);

  while (q.size()) {
    auto u = q.front();
    q.pop();
    v[u] = true;
    for (auto w : g[u]) if (!v[w]) q.push(w);
  }

  for (int i = 0; i < n; i++) {
    if (g[i].size() != 2 or !v[i]) {
      cout << "No" << endl;
      exit(0);
    }
  }

  cout << "Yes" << endl;

  return 0;
}

Submission Info

Judge Result