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Submission #799662

# Submission time Handle Problem Language Result Execution time Memory
799662 2023-07-31T18:15:52 Z GusterGoose27 Parking (CEOI22_parking) C++17
20 / 100
 83 ms 17376 KB 
#include <bits/stdc++.h>

using namespace std;

const int MAXN = 2e5+5;
int n, m;
vector<int> config[MAXN];
int inv[2*MAXN]; // 2*i+0 for bottom 1 for top
bool vis[MAXN];

typedef pair<int, int> pii;

vector<pii> res;
set<int> avail;

int get_empty() {
	if (avail.empty()) {
		// assert(false);
		cout << -1 << endl;
		exit(0);
	}
	return *avail.begin();
}

void move(int a, int b) {
	assert(config[a].size());
	assert(config[b].size() < 2);
	assert(config[b].empty() || config[a].back() == (config[b].back()^1));

	res.push_back(pii(a+1, b+1));
	if (config[b].empty()) avail.erase(b);
	config[b].push_back(config[a].back());
	config[a].pop_back();
	if (config[a].empty()) avail.insert(a);
	inv[config[b].back()] = 2*b+config[b].size()-1;
}

void dfs(int cur, bool picky = 0) {
	int v = config[cur][0];
	int p = inv[v^1]/2;
	if (config[p].size() == 1) {
		move(p, cur);
		return;
	}
	if (inv[v^1]&1) {
		move(p, cur);
		return dfs(p, picky);
	}
	if (picky) return;
	// if we are going to be picky, then we might as well do it from the other direction
	int s = p;
	vector<pii> qu;
	while (config[s].size() == 2 && !(inv[config[s][1]^1] & 1)) {
		int nxt = inv[config[s][1]^1]/2;
		qu.push_back(pii(s, nxt));
		s = nxt;
	}
	if (config[s].size() == 2) {
		int e = get_empty();
		move(s, e);
		s = e;
	}
	for (int i = qu.size()-1; i >= 0; i--) move(qu[i].first, qu[i].second);
	move(p, cur);
	if (config[s].size() == 1) dfs(s, picky);
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(NULL);
	cin >> n >> m;
	for (int i = 0; i < m; i++) {
		int x, y; cin >> x >> y;
		if (x > 0) {
			config[i].push_back(2*(x-1)+vis[x-1]);
			vis[x-1] = 1;
		}
		if (y > 0) {
			config[i].push_back(2*(y-1)+vis[y-1]);
			vis[y-1] = 1;
		}
	}
	for (int i = 0; i < m; i++) {
		for (int j = 0; j < config[i].size(); j++) {
			inv[config[i][j]] = 2*i+j;
		}
		if (config[i].empty()) avail.insert(i);
	}
	// first step: combine anything that can be combined without extra space usage
	/*
	Clearly, this will only be possible if we have two endpoints that can just be simply connected
	(i.e)
	a
	b a
	c b
	d c
	d
	*/
	for (int i = 0; i < m; i++) {
		if (config[i].size() == 1) {
			dfs(i, 1);
		}
	}

	// now, for each single bottom, combine it (again, this frees space).
	// this will always take exactly 1 empty spot, so this is the best option
	for (int i = 0; i < m; i++) {
		if (config[i].size() == 1) {
			dfs(i);
		}
	}
	// nothing else will free up space, so order no longer matters
	// everything from here onwards should be ok due to subtask 2
	for (int i = 0; i < m; i++) {
		if (config[i].empty()) continue;
		assert(config[i].size() == 2);
		if (config[i][0] == (config[i][1]^1)) continue;
		int e = get_empty();
		move(i, e);
		dfs(i, 0);
	}
	for (int i = 0; i < m; i++) assert(config[i].empty() || (config[i].size() == 2 && (config[i][0]^1) == config[i][1]));
	cout << res.size() << '\n';
	for (pii p: res) {
		cout << p.first << ' ' << p.second << '\n';
	}
}

Compilation message

Main.cpp: In function 'int main()':
Main.cpp:83:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   83 |   for (int j = 0; j < config[i].size(); j++) {
      |                   ~~^~~~~~~~~~~~~~~~~~

Subtask #1
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 4936 KB Output is correct
2 Correct 2 ms 4948 KB Output is correct
3 Correct 2 ms 4948 KB Output is correct
4 Correct 2 ms 4948 KB Output is correct
5 Correct 2 ms 4948 KB Output is correct
6 Correct 2 ms 4948 KB Output is correct
7 Correct 2 ms 4948 KB Output is correct
8 Correct 2 ms 4948 KB Output is correct
9 Correct 2 ms 4948 KB Output is correct
10 Correct 2 ms 4948 KB Output is correct

Subtask #2
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 77 ms 16852 KB Output is correct
2 Correct 83 ms 17140 KB Output is correct
3 Correct 71 ms 16196 KB Output is correct
4 Correct 69 ms 16072 KB Output is correct
5 Correct 82 ms 17376 KB Output is correct

Subtask #3
0.0 / 25.0

# Verdict Execution time Memory Grader output
1 Incorrect 2 ms 5076 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #4
0.0 / 15.0

# Verdict Execution time Memory Grader output
1 Incorrect 2 ms 5076 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #5
0.0 / 25.0

# Verdict Execution time Memory Grader output
1 Incorrect 3 ms 5076 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #6
0.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 3 ms 4936 KB Output is correct
2 Correct 2 ms 4948 KB Output is correct
3 Correct 2 ms 4948 KB Output is correct
4 Correct 2 ms 4948 KB Output is correct
5 Correct 2 ms 4948 KB Output is correct
6 Correct 2 ms 4948 KB Output is correct
7 Correct 2 ms 4948 KB Output is correct
8 Correct 2 ms 4948 KB Output is correct
9 Correct 2 ms 4948 KB Output is correct
10 Correct 2 ms 4948 KB Output is correct
11 Correct 77 ms 16852 KB Output is correct
12 Correct 83 ms 17140 KB Output is correct
13 Correct 71 ms 16196 KB Output is correct
14 Correct 69 ms 16072 KB Output is correct
15 Correct 82 ms 17376 KB Output is correct
16 Incorrect 2 ms 5076 KB Output isn't correct
17 Halted 0 ms 0 KB -