Submission #968763

#	Time	Username	Problem	Language	Result	Execution time	Memory
968763		marvinthang	Parking (CEOI22_parking)	C++17	100 / 100	288 ms	45480 KiB

Main

/*************************************
*    author: marvinthang             *
*    created: 24.04.2024 10:00:00    *
*************************************/

#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;
	vector <int> bot(m), top(m);
	vector pos(n + 1, vector(2, -1));
	vector <vector <int>> adj(m << 1);
	vector <int> emp;
	vector <int> sz(m);
	REP(i, m) {
		cin >> bot[i] >> top[i];
		if (bot[i]) {
			++sz[i];
			pos[bot[i]][pos[bot[i]][0] != -1] = i << 1;
			if (top[i]) {
				++sz[i];
				pos[top[i]][pos[top[i]][0] != -1] = i << 1 | 1;
				if (bot[i] != top[i]) {
					adj[i << 1].push_back(i << 1 | 1);
					adj[i << 1 | 1].push_back(i << 1);
				}
			}
		} else emp.push_back(i);
	}
	auto get_empty = [&] {
		while (!emp.empty() && sz[emp.back()]) emp.pop_back();
		if (emp.empty()) {
			cout << "-1\n";
			exit(0);
		}
		return emp.back();
	};
	FORE(i, 1, n) if (pos[i][0] != (pos[i][1] ^ 1)) {
		adj[pos[i][0]].push_back(pos[i][1]);
		adj[pos[i][1]].push_back(pos[i][0]);
	}
	vector <pair <int, int>> res;
	auto move = [&] (int x, int y) {
		x >>= 1; y >>= 1;
		res.emplace_back(x, y);
		if (!--sz[x]) emp.push_back(x);
		++sz[y];
	};
	auto solve_path = [&] (vector <int> &path) {
		for (int i = 0; i < (int) path.size(); i += 2) {
			if (path[i + 1] & 1) move(path[i + 1], path[i]);
			else {
				int p = path.size();
				for (int j = i; j < (int) path.size(); j += 2) if ((path[j] & 1) && (path[j + 1] & 1)) {
					p = j;
					break;
				}
				if (p < (int) path.size()) {
					int x = get_empty() << 1;
					move(path[p], x);
					move(path[p + 1], x);
				}
				for (int j = p - 2; j >= i; j -= 2) move(path[j], path[j + 1]);
				i = p;
			}
		}
	};
	vector <bool> used(m << 1);
	vector <vector <int>> paths, cycles;
	vector <int> cnt_pt;
	REP(i, m + m) if (!used[i] && (int) adj[i].size() == 1) {
		used[i] = true;
		vector <int> path {i};
		int u = i, p = -1;
		while (p == -1 || (int) adj[u].size() == 2) {
			tie(p, u) = pair{u, adj[u][adj[u][0] == p]};
			used[u] = true;
			path.push_back(u);
		}
		int cnt = 0;
		for (int i = 0; i < (int) path.size(); i += 2) if ((path[i] & 1) && (path[i + 1] & 1)) ++cnt;
		paths.push_back(path);
		cnt_pt.push_back(cnt);
	}
	vector <int> order(paths.size());
	iota(ALL(order), 0);
	sort(ALL(order), [&] (int x, int y) { return cnt_pt[x] < cnt_pt[y]; });
	for (int i: order) solve_path(paths[i]);
	auto del_edge = [&] (int x, int y) {
		adj[x].erase(find(ALL(adj[x]), y));
		adj[y].erase(find(ALL(adj[y]), x));
	};
	auto solve_cycle = [&] (vector <int> &cycle) {
		int p = -1;
		for (int i = 0; i + 1 < (int) cycle.size(); ++i) if ((cycle[i] & 1) && (cycle[i + 1] & 1)) {
			p = i;
			break;
		}
		if (p != -1) {
			int x = get_empty() << 1;
			move(cycle[p], x);
			move(cycle[p + 1], x);
			del_edge(!p ? cycle.end()[-2] : cycle[p - 1], cycle[p]);
			del_edge(cycle[p], cycle[p + 1]);
			del_edge(cycle[p + 1], p + 2 == (int) cycle.size() ? cycle[1] : cycle[p + 2]);
			cycle.pop_back();
			cycle.erase(cycle.begin() + p);
			if (p == (int) cycle.size()) cycle.erase(cycle.begin());
			else cycle.erase(cycle.begin() + p);
			rotate(cycle.begin(), cycle.begin() + p, cycle.end());
			solve_path(cycle);
		} else {
			cycle.pop_back();
			if (cycle[0] & 1) rotate(cycle.begin(), cycle.begin() + 1, cycle.end());
			if (cycle[0] == (cycle[1] ^ 1)) {
				rotate(cycle.begin(), cycle.begin() + 1, cycle.end());
				reverse(ALL(cycle));
			}
			int x = get_empty() << 1;
			move(cycle.back(), x);
			for (int i = 1; i + 2 < (int) cycle.size(); i += 2) move(cycle[i], cycle[i - 1]);
			move(cycle.end()[-2], x);
		}
	};
	REP(i, m + m) if (!used[i] && (int) adj[i].size() == 2) {
		vector <int> cycle;
		int u = i, p = -1;
		while (!used[u]) {
			used[u] = true;
			cycle.push_back(u);
			tie(p, u) = pair{u, adj[u][adj[u][0] == p]};
		}
		int cnt = 0;
		cycle.push_back(cycle[0]);
		for (int i = 0; i + 1 < (int) cycle.size(); ++i) if ((cycle[i] & 1) && (cycle[i + 1] & 1)) ++cnt;
		cycles.push_back(cycle);
		cnt_pt.push_back(cnt);
	}
	order.resize(cycles.size());
	iota(ALL(order), 0);
	sort(ALL(order), [&] (int x, int y) { return cnt_pt[x] < cnt_pt[y]; });
	for (int i: order) solve_cycle(cycles[i]);

	cout << res.size() << '\n';
	for (auto [x, y]: res) cout << x + 1 << ' ' << y + 1 << '\n';
}

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

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.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); }
      |                                                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:187:2: note: in expansion of macro 'file'
  187 |  file("parking");
      |  ^~~~
Main.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); }
      |                                                                                       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:187:2: note: in expansion of macro 'file'
  187 |  file("parking");
      |  ^~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 15 / 15
• Subtask 5: 25 / 25
• Subtask 6: 15 / 15