Submission #659818

#	Time	Username	Problem	Language	Result	Execution time	Memory
659818		Sohsoh84	Newspapers (CEOI21_newspapers)	C++17	100 / 100	1 ms	468 KiB

newspapers

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> pll;

#define all(x)			(x).begin(),(x).end()
#define X			first
#define Y			second
#define sep			' '
#define endl			'\n'
#define debug(x)		cerr << #x << ": " <<  x << endl;

const ll MAXN = 1e3 + 10;

int n, m, dist[MAXN], par[MAXN], D[MAXN];
vector<int> adj[MAXN], diam, ans;

void dfs(int v) {
	dist[v] = dist[par[v]] + 1;
	D[v] = 1;
	for (int u : adj[v]) {
		if (u != par[v]) {
			par[u] = v;
			dfs(u);
			D[v] = max(D[v], D[u] + 1);
		}
	}
}

inline void add(int v) {
	int m = ans.size();
	if (m >= 2 && ans[m - 1] == v && ans[m - 2] == v) {
		ans.pop_back();
		ans.pop_back();
	}
	
	ans.push_back(v);
}

inline void dojob() {
	int m = diam.size();
	diam.push_back(-1);
	int i = 0;
	for (i = 0; i < m; i++) {
		int v = diam[i];
		add(v);
		for (int u : adj[v]) {
			if (u == par[v] || u == diam[i + 1]) continue;
			if (D[u] >= 2) {
				cout << "NO" << endl;
				exit(0);
			}
			
			add(u);
			add(v);
		}
	}
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	cin >> n >> m;
	if (m >= n) return cout << "NO" << endl, 0;

	if (n == 1) return cout << "YES" << endl << 1 << endl << 1 << endl, 0;
	if (n == 2) return cout << "YES" << endl << 2 << endl << 1 << sep << 1 << endl, 0;

	for (int i = 1; i <= m; i++) {
		int u, v;
		cin >> u >> v;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}

	int rt = 0;
	vector<int> vec;
	for (int i = 1; i <= n; i++) {
		if (adj[i].size() == 1)
			vec.push_back(i);
		else rt = i;
	}

	for (int e : vec)
		for (int u : adj[e])
			adj[u].erase(find(all(adj[u]), e));

	dfs(rt);
	int v = max_element(dist, dist + MAXN) - dist;
	
	memset(par, 0, sizeof par);
	memset(dist, 0, sizeof dist);
	dfs(v);
	v = max_element(dist, dist + MAXN) - dist;
	
	while (v) {
		diam.push_back(v);
		v = par[v];
	}

	reverse(all(diam));
	dojob();

	int m = ans.size();
	while (m--) ans.push_back(ans[m]);

	cout << "YES" << endl << ans.size() << endl;
	for (int e : ans) cout << e << sep;
	cout << endl;
	return 0;
}

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