Submission #4673262

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define _MACRO(_1, _2, _3, NAME, ...) NAME
#define _repl(i,a,b) for(int i=(int)(a);i<(int)(b);i++)
#define _rep(i,n) _repl(i,0,n)
#define rep(...) _MACRO(__VA_ARGS__, _repl, _rep)(__VA_ARGS__)
#define pb push_back
#define all(x) begin(x),end(x)
#define uniq(x) sort(all(x)),(x).erase(unique(all(x)),end(x))
#ifdef LOCAL
#define dbg(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
void _dbg(string){cerr<<endl;}
template<class H,class... T> void _dbg(string s,H h,T... t){int l=s.find(',');cerr<<s.substr(0,l)<<" = "<<h<<", ";_dbg(s.substr(l+1),t...);}
template<class T,class U> ostream& operator<<(ostream &o, const pair<T,U> &p){o<<"("<<p.first<<","<<p.second<<")";return o;}
template<class T> ostream& operator<<(ostream &o, const vector<T> &v){o<<"[";for(T t:v){o<<t<<",";}o<<"]";return o;}
#else
#define dbg(...) {}
#endif

set<int> cur;

set<int> hoge[2];

set<int> g[100005];

const int OK = 2000000;
const int NG = -1;

int dfs(int v, int from = -1){
  cur.insert(v);

  for(auto to : g[v]) if(to != from){
    int r = -1;
    if(cur.count(to) == 1) {
      r = to;
    }
    else {
      r = dfs(to, v);
    }
    if(r == OK){ return OK; }
    if(r > -1){
      hoge[0].insert(v);
      g[v].erase(to);
      g[to].erase(v);
      if(r == v) return OK;
      else return r;
    }
    if(r == NG) return NG;
  }
  return NG;
}

bool solve(){
  int n,m;
  cin>>n>>m;
  rep(i,m){
    int a,b;
    cin>>a>>b;
    a--;b--;
    g[a].insert(b);
    g[b].insert(a);
  }

  int cnt = 0;
  rep(i,n){
    while(g[i].size() > 0) {
      cur.clear();
      int r = dfs(i);
      if(r == OK) {
        cnt++;
        swap(hoge[0], hoge[1]);
      }
      else {
        assert(r == NG);
        return false;
      }
    }
  }

  if(cnt == 2) {
    int xx = 0;
    for(auto x : hoge[0]) if(hoge[1].count(x) ==1 ) xx++;
    if(xx>=3) cnt++;
  }

  return cnt >= 3;
}

int main(){
  cout << (solve() ? "Yes" : "No") << endl;
  return 0;
}

Submission Info

Judge Result