Submission #624681

#	Time	Username	Problem	Language	Result	Execution time	Memory
624681		iomoon191	Newspapers (CEOI21_newspapers)	C++17	100 / 100	1 ms	468 KiB

newspapers

#include <bits/stdc++.h>
using ll = long long;
#define int ll
using namespace std;

#define sz(x) (int)(x).size()
#define foru(i, l, r) for(int i = l; i <= r; i++)
#define ford(i, l, r) for(int i = l; i >= r; i--)
#define fi first
#define se second
#define mod 998244353

#define db(x) cerr << __LINE__ << " " << #x << " " << x << "\n"
using vi = vector<int>;
using pi = pair<int, int>;

const ll N = 1005;
const ll inf = 1e18;

int n, m, par[N];
vi adj[N];
bool ok[N], used[N];

pi dfs(int u, int p = -1){
	pi res(0, u);
	for(auto &i : adj[u]){
		if(i == p) continue;
		par[i] = u;
		pi j = dfs(i, u);
		j.fi++;
		res = max(res, j);
	}
	return res;
}

void solve(){
	cin >> n >> m;
	if(n == 1){
		cout << "YES\n1\n1";
		return;
	}
	if(n == 2){
		cout << "YES\n2\n1 1";
		return;
	}
	if(m != n - 1){
		cout << "NO";
		return;
	}
	foru(i, 1, m){
		int u, v; 
		cin >> u >> v;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	int x = dfs(1).se;
	int y = dfs(x).se;
	for(int i = y; ; i = par[i]){
		ok[i] = true;
		used[i] = true;
		for(auto &j : adj[i]){
			ok[j] = true;
			for(auto &k : adj[j]){
				ok[k] = true;
			}
		}
		if(i == x) break;
 	}
 	if(count(ok + 1, ok + n + 1, 0)){
 		cout << "NO";
 		return;
 	}
 	vi res;
 	for(int i = par[y]; i != x; i = par[i]){
 		res.push_back(i);
 		for(auto &j : adj[i]){
 			if(used[j] or sz(adj[j]) == 1){
 				continue;
 			}
 			res.push_back(j);
 			res.push_back(i);
 		}
 	}
 	cout << "YES\n" << (sz(res) << 1) << "\n";
 	foru(i, 0, sz(res) - 1) cout << res[i] << " ";
 	ford(i, sz(res) - 1, 0) cout << res[i] << " ";
}

signed main(){
	ios_base::sync_with_stdio(0); cin.tie(0);
	int t = 1; 
	while(t--){
		solve();
	}
}

• Subtask 1: 12 / 12
• Subtask 2: 8 / 8
• Subtask 3: 80 / 80