Submission #792113

#	Time	Username	Problem	Language	Result	Execution time	Memory
792113		kwongweng	Newspapers (CEOI21_newspapers)	C++17	0 / 100	1 ms	352 KiB

newspapers

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef long double ld;
typedef pair<ll, ll> pll;
#define FOR(i, a, b) for(int i = a; i < b; i++)
#define ROF(i, a, b) for(int i = a; i >= b; i--)
#define ms memset
#define pb push_back
#define fi first
#define se second

vi g[1001];
vi d(1001), mxd(1001), p(1001);
// mxd[u] - max d[v] for v in subtree u

void dfs(int u){
	mxd[u] = d[u];
	for (int v : g[u]){
		if (p[u]==v) continue;
		p[v] = u; d[v]=d[u]+1;
		dfs(v);
		mxd[u] = max(mxd[u], mxd[v]);
	}
}

void solve(){
	int n, m; cin >> n >> m;
	FOR(i,0,m){
		int u, v; cin >> u >> v;
		g[u].pb(v);
		g[v].pb(u);
	}
	if (m>n-1){
		cout << "NO\n";
		return;
	}
	int a=1, b=1; // longest path
	int mx = 0;
	FOR(u,1,n+1){
		FOR(i,1,n+1){
			d[i]=0; p[i]=0; mxd[i]=0;
		}
		dfs(u);
		if (mxd[u] > mx){
			a = u; mx = mxd[u];
			FOR(v,1,n+1){
				if (d[v] == mxd[u]){
					b = v; break;
				}
			}
		}
		int cnt = 0;
		for (int v : g[u]){
			if (mxd[v] >= 3){
				cnt++;
			}
		}
		if (cnt >= 3){
			cout << "NO\n";
			return;
		}
	}
	cout << "YES\n";
	if (n==1){
		cout << 1 << '\n' << 1 << '\n';
		return;
	}
	if (n==2){
		cout << 2 << '\n' << 1 << " " << 1 << '\n';
		return;
	}
	FOR(i,1,n+1){
		d[i]=0; p[i]=0; mxd[i]=0;
	}
	dfs(a);
	vi ans;
	while (p[b] != a){
		int c = p[b];
		ans.pb(c);
		for (int u : g[c]){
			if (u == b || p[c] == u) continue;
			if (g[u].size()>=2){
				ans.pb(u);
				ans.pb(c);
			}
		}
		b = c;
	}
	cout << 2*ans.size() << '\n';
	FOR(i,0,n) cout << ans[i] << " ";
	ROF(i,n-1,0) cout << ans[i] << " ";
	cout << '\n';
}

int main(){
    ios::sync_with_stdio(false);
    if (fopen("input.txt", "r")) {
		freopen("input.txt", "r", stdin);
		freopen("output.txt", "w", stdout);
	}
    int TC = 1;
    //cin >> TC;
    FOR(i, 1, TC+1){
        //cout << "Case #" << i << ": ";
        solve();
    }
	
	return 0;
}

Compilation message (stderr)

newspapers.cpp: In function 'int main()':
newspapers.cpp:103:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  103 |   freopen("input.txt", "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
newspapers.cpp:104:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  104 |   freopen("output.txt", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 12
• Subtask 2: 0 / 8
• Subtask 3: 0 / 80