Submission #65462733

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Source Code Expand

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <vector>
#include <queue>
#include <cmath>
#include <stack>
#include <ctime>
#include <map>
#include <set>

#define rall(x) (x).rbegin(), (x).rend()
#define all(x) (x).begin(), (x).end()
#define _sz(x) ((int)x.size())
#define pii pair<int, int>
#define mpair make_pair
#define ld long double
#define vi vector<int>
#define ll long long
#define ss second
#define ff first

using namespace std;

const ll lINF = 1000000000000000007;
const int iINF = 1000000007;
const int INF = 1e5+1;

/*
*/
// 

vector<int> g;
vector<vector<int>> gr;
vector<bool> visited;

void dfs(int cur) {
    visited[cur] = true;
    for(int neighbor : gr[cur]) {
        if(!visited[neighbor]) dfs(neighbor);
    }
}


void solve(){
    int n, m;   
    cin >> n >> m;
    g.resize(n+1);
    gr.resize(n+1);
    visited.resize(n+1);

    for(int i = 0; i < m; ++ i){
        int x, y;
        cin >> x >> y; 
        gr[x].push_back(y);
        gr[y].push_back(x);
        g[x] ++;
        g[y] ++;
    }

    bool l = false;
    for(int i = 1; i <= n; ++ i){
        if(g[i] != 2){
            l = true;
            break;
        }
    }
    if(l){
        cout << "No";
        return ;
    }

    dfs(1);

    for(int i = 1; i <= n; ++ i){
        if(!visited[i]){
            cout << "No";
            return ;
        }
    }

    cout << "Yes";

}


int main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	int tt = 1; 
	// cin >> tt;
	while(tt --){
		solve();
		cout << '\n';
	}
	
	return 0;	
}

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