Submission #576345

#	Time	Username	Problem	Language	Result	Execution time	Memory
576345		acatmeowmeow	Mecho (IOI09_mecho)	C++11	100 / 100	662 ms	13036 KiB

mecho

#include <bits/stdc++.h>

using namespace std;

#define int long long 

const int N = 8e2 + 5;
int n, s;
char grid[N][N];
pair<int, int> init, home;
vector<pair<int, int>> hive;

vector<int> dx = {-1, 0, 1, 0}, dy = {0, 1, 0, -1};
queue<pair<int, int>> qmecho, qbee;
bool vmecho[N][N], vbee[N][N];
int dmecho[N][N], dbee[N][N];

bool bee_inbound(int x, int y) {
	return x >= 1 && x <= n && y >= 1 && y <= n && !vbee[x][y] && (grid[x][y] == 'G' || grid[x][y] == 'M');
}

bool mecho_inbound(int x, int y) {
	return x >= 1 && x <= n && y >= 1 && y <= n && !vmecho[x][y] && (grid[x][y] == 'G' || grid[x][y] == 'D');
}

bool valid(int m) {
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			vmecho[i][j] = vbee[i][j] = false;
			dmecho[i][j] = dbee[i][j] = 1e18;
		}
	}
	for (auto&b : hive) {
		int x = b.first, y = b.second;
		dbee[x][y] = 0, vbee[x][y] = true, qbee.push(b);
	}
	while (qbee.size()) {
		int x = qbee.front().first, y = qbee.front().second; qbee.pop();
		for (int k = 0; k < 4; k++) {
			int tox = x + dx[k], toy = y + dy[k];
			if (!bee_inbound(tox, toy)) continue;
			dbee[tox][toy] = dbee[x][y] + 1, vbee[tox][toy] = true, qbee.push({tox, toy});
		}
	}
	int x = init.first, y = init.second;
	dmecho[x][y] = 0, vmecho[x][y] = true, qmecho.push({x, y});
	while (qmecho.size()) {
		int x = qmecho.front().first, y = qmecho.front().second; qmecho.pop();
		if (dmecho[x][y]/s >= dbee[x][y] - m) continue;
		for (int k = 0; k < 4; k++) {
			int tox = x + dx[k], toy = y + dy[k];
			if (!mecho_inbound(tox, toy)) continue;
			dmecho[tox][toy] = dmecho[x][y] + 1, vmecho[tox][toy] = true, qmecho.push({tox, toy});
		}
	}
	x = home.first, y = home.second;
	return vmecho[x][y] && dmecho[x][y]/s < dbee[x][y] - m;
}

signed main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cin >> n >> s;
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			cin >> grid[i][j];
			if (grid[i][j] == 'M') init = {i, j};
			else if(grid[i][j] == 'D') home = {i, j};
			else if(grid[i][j] == 'H') hive.push_back({i, j});
		}
	}
	int l = 0, r = n*n, ans = -1;
	while (l <= r) {
		int m = (l + r)/2;
		if (valid(m)) ans = m, l = m + 1;
		else r = m - 1;
	}
	cout << ans << '\n';
	return 0;
}

• Subtask 1: 100 / 100