Submission #970849

#	Time	Username	Problem	Language	Result	Execution time	Memory
970849		marvinthang	Newspapers (CEOI21_newspapers)	C++17	100 / 100	1 ms	1012 KiB

newspapers

/*************************************
*    author: marvinthang             *
*    created: 27.04.2024 18:08:42    *
*************************************/

#include <bits/stdc++.h>

using namespace std;

#define                  fi  first
#define                  se  second
#define                left  ___left
#define               right  ___right
#define                TIME  (1.0 * clock() / CLOCKS_PER_SEC)
#define             MASK(i)  (1LL << (i))
#define           BIT(x, i)  ((x) >> (i) & 1)
#define  __builtin_popcount  __builtin_popcountll
#define              ALL(v)  (v).begin(), (v).end()
#define           REP(i, n)  for (int i = 0, _n = (n); i < _n; ++i)
#define          REPD(i, n)  for (int i = (n); i-- > 0; )
#define        FOR(i, a, b)  for (int i = (a), _b = (b); i < _b; ++i) 
#define       FORD(i, b, a)  for (int i = (b), _a = (a); --i >= _a; ) 
#define       FORE(i, a, b)  for (int i = (a), _b = (b); i <= _b; ++i) 
#define      FORDE(i, b, a)  for (int i = (b), _a = (a); i >= _a; --i) 
#define        scan_op(...)  istream & operator >> (istream &in, __VA_ARGS__ &u)
#define       print_op(...)  ostream & operator << (ostream &out, const __VA_ARGS__ &u)
#ifdef LOCAL
    #include "debug.h"
#else
    #define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
    #define DB(...) 23
    #define db(...) 23
    #define debug(...) 23
#endif

template <class U, class V> scan_op(pair <U, V>)  { return in >> u.first >> u.second; }
template <class T> scan_op(vector <T>)  { for (size_t i = 0; i < u.size(); ++i) in >> u[i]; return in; }
template <class U, class V> print_op(pair <U, V>)  { return out << '(' << u.first << ", " << u.second << ')'; }
template <size_t i, class T> ostream & print_tuple_utils(ostream &out, const T &tup) { if constexpr(i == tuple_size<T>::value) return out << ")";  else return print_tuple_utils<i + 1, T>(out << (i ? ", " : "(") << get<i>(tup), tup); }
template <class ...U> print_op(tuple<U...>) { return print_tuple_utils<0, tuple<U...>>(out, u); }
template <class Con, class = decltype(begin(declval<Con>()))> typename enable_if <!is_same<Con, string>::value, ostream&>::type operator << (ostream &out, const Con &con) { out << '{'; for (__typeof(con.begin()) it = con.begin(); it != con.end(); ++it) out << (it == con.begin() ? "" : ", ") << *it; return out << '}'; }

// end of template

void process(void) {
	int n, m; cin >> n >> m;
	if (n == 1) return void(cout << "YES\n1\n1\n");
	if (n == 2) return void(cout << "YES\n2\n1 1\n");
	if (m != n - 1) return void(cout << "NO\n");
	vector <vector <int>> adj(n);
	REP(i, m) {
		int u, v; cin >> u >> v; --u; --v;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	vector <int> dist(n), par(n);
	auto bfs = [&] (int s) {
		fill(ALL(dist), -1);
		dist[s] = 0;
		queue <int> q;
		q.push(s);
		while (!q.empty()) {
			int u = q.front(); q.pop();
			for (int v: adj[u]) if (dist[v] == -1) {
				dist[v] = dist[u] + 1;
				par[v] = u;
				q.push(v);
			}
		}
		return max_element(ALL(dist)) - dist.begin();
	};
	int a = bfs(0);
	int b = bfs(a);
	vector <int> path;
	while ((b = par[b]) != a) path.push_back(b);
	vector <int> res;
	REP(i, path.size()) {
		int u = path[i];
		res.push_back(u);
		if (i && i + 1 < (int) path.size()) {
			for (int v: adj[u]) if (v != path[i - 1] && v != path[i + 1] && (int) adj[v].size() > 1) {
				for (int w: adj[v]) if (w != u && (int) adj[w].size() > 1) return void(cout << "NO\n");
				res.push_back(v);
				res.push_back(u);
			}
		}
	}
	int sz = res.size();
	res.resize(sz + sz);
	reverse_copy(res.begin(), res.begin() + sz, res.begin() + sz);
	cout << "YES\n" << res.size() << '\n';
	for (int x: res) cout << x + 1 << ' ';
}

int main(void) {
	ios_base::sync_with_stdio(false); cin.tie(nullptr); // cout.tie(nullptr);
	file("newspapers");
	// int t; cin >> t; while (t--)
	process();
	// cerr << "Time elapsed: " << TIME << " s.\n";
	return (0^0);
}

Compilation message (stderr)

newspapers.cpp: In function 'int main()':
newspapers.cpp:30:61: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   30 |     #define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
newspapers.cpp:97:2: note: in expansion of macro 'file'
   97 |  file("newspapers");
      |  ^~~~
newspapers.cpp:30:94: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   30 |     #define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
      |                                                                                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
newspapers.cpp:97:2: note: in expansion of macro 'file'
   97 |  file("newspapers");
      |  ^~~~

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