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Submission #1005371

# Submission time Handle Problem Language Result Execution time Memory
1005371 2024-06-22T11:19:18 Z Braabebo10 Mecho (IOI09_mecho) C++14
100 / 100
 412 ms 7516 KB 
#include <bits/stdc++.h>
using namespace std;

const int MAX_N = 800;
vector<string> field(MAX_N);
int n, s;

bool valid_sq(int x, int y) {
	return x >= 0 && x < n && y >= 0 && y < n &&
	       (field[x][y] == 'G' || field[x][y] == 'M');
}

bool mecho_reached(int mecho_dis, int bees_dis) {
	return mecho_dis / s < bees_dis;
}

int main() {
	cin >> n >> s;
	for (int i = 0; i < n; i++) { cin >> field[i]; }

	vector<pair<int, int>> hives;
	int mechox, mechoy, home_x, home_y;
	// find x and y coordinates for for Mecho, the bees and the cave
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			if (field[i][j] == 'M') {
				mechox = i;
				mechoy = j;
			} else if (field[i][j] == 'H') {
				hives.push_back({i, j});
			} else if (field[i][j] == 'D') {
				home_x = i;
				home_y = j;
			}
		}
	}

	int dx[] = {-1, 0, 1, 0};
	int dy[] = {0, -1, 0, 1};

	// binary search on waiting time
	int l = 0;
	int r = n * n;
	while (l <= r) {
		vector<vector<bool>> bees_visited(n, vector<bool>(n));
		vector<vector<bool>> mecho_visited(n, vector<bool>(n));
		vector<vector<int>> bees_time(n, vector<int>(n));
		vector<vector<int>> mecho_time(n, vector<int>(n));
		queue<pair<int, int>> q;

		int eating_time = (l + r) / 2;

		// move bees
		for (auto i : hives) {
			q.push({i.first, i.second});
			bees_visited[i.first][i.second] = true;
		}

		while (!q.empty()) {
			int x = q.front().first, y = q.front().second;
			q.pop();
			for (int i = 0; i < 4; i++) {
				int nx = x + dx[i], ny = y + dy[i];
				if (valid_sq(nx, ny) && !bees_visited[nx][ny]) {
					bees_time[nx][ny] = bees_time[x][y] + 1;
					q.push({nx, ny});
					bees_visited[nx][ny] = true;
				}
			}
		}

		// move Mecho
		q.push({mechox, mechoy});
		mecho_visited[mechox][mechoy] = true;
		if (bees_time[mechox][mechoy] <= eating_time) { q.pop(); }

		while (!q.empty()) {
			int x = q.front().first, y = q.front().second;
			q.pop();
			for (int i = 0; i < 4; i++) {
				int nx = x + dx[i], ny = y + dy[i];
				/*
				 * check if mecho reaces node[x][y] before the bees
				 * divide the time mecho takes to reach a node by s, since
				 * mecho walks s steps at a time.
				 * substract the eating time from the time taken for the
				 * bees to reach the node, because that time was used by
				 * mecho for eating
				 */
				if (valid_sq(nx, ny) && !mecho_visited[nx][ny] &&
				    mecho_reached(mecho_time[x][y] + 1,
				                  bees_time[nx][ny] - eating_time)) {
					mecho_visited[nx][ny] = true;
					q.push({nx, ny});
					mecho_time[nx][ny] = mecho_time[x][y] + 1;
				}
			}
		}

		// check if mecho reached a node surrounding his cave before the bees
		bool reached = false;
		for (int i = 0; i < 4; i++) {
			int nx = home_x + dx[i], ny = home_y + dy[i];
			if (valid_sq(nx, ny) &&
			    mecho_reached(mecho_time[nx][ny],
			                  bees_time[nx][ny] - eating_time) &&
			    mecho_visited[nx][ny]) {
				reached = true;
			}
		}
		if (reached) {
			l = eating_time + 1;
		} else {
			r = eating_time - 1;
		}
	}

	cout << l - 1 << '\n';
}

Compilation message

mecho.cpp: In function 'int main()':
mecho.cpp:74:31: warning: 'mechoy' may be used uninitialized in this function [-Wmaybe-uninitialized]
   74 |   mecho_visited[mechox][mechoy] = true;
      |                               ^
mecho.cpp:74:23: warning: 'mechox' may be used uninitialized in this function [-Wmaybe-uninitialized]
   74 |   mecho_visited[mechox][mechoy] = true;
      |                       ^
mecho.cpp:103:29: warning: 'home_y' may be used uninitialized in this function [-Wmaybe-uninitialized]
  103 |    int nx = home_x + dx[i], ny = home_y + dy[i];
      |                             ^~
mecho.cpp:103:8: warning: 'home_x' may be used uninitialized in this function [-Wmaybe-uninitialized]
  103 |    int nx = home_x + dx[i], ny = home_y + dy[i];
      |        ^~

Subtask #1
100.0 / 100.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 0 ms 348 KB Output is correct
6 Correct 0 ms 348 KB Output is correct
7 Correct 310 ms 7228 KB Output is correct
8 Correct 0 ms 348 KB Output is correct
9 Correct 0 ms 348 KB Output is correct
10 Correct 0 ms 348 KB Output is correct
11 Correct 0 ms 348 KB Output is correct
12 Correct 1 ms 348 KB Output is correct
13 Correct 1 ms 460 KB Output is correct
14 Correct 2 ms 348 KB Output is correct
15 Correct 0 ms 348 KB Output is correct
16 Correct 0 ms 348 KB Output is correct
17 Correct 0 ms 348 KB Output is correct
18 Correct 0 ms 392 KB Output is correct
19 Correct 1 ms 604 KB Output is correct
20 Correct 0 ms 348 KB Output is correct
21 Correct 1 ms 604 KB Output is correct
22 Correct 1 ms 348 KB Output is correct
23 Correct 1 ms 348 KB Output is correct
24 Correct 1 ms 348 KB Output is correct
25 Correct 1 ms 348 KB Output is correct
26 Correct 1 ms 348 KB Output is correct
27 Correct 1 ms 348 KB Output is correct
28 Correct 1 ms 348 KB Output is correct
29 Correct 1 ms 348 KB Output is correct
30 Correct 1 ms 348 KB Output is correct
31 Correct 2 ms 460 KB Output is correct
32 Correct 1 ms 344 KB Output is correct
33 Correct 28 ms 1796 KB Output is correct
34 Correct 27 ms 1800 KB Output is correct
35 Correct 62 ms 1624 KB Output is correct
36 Correct 37 ms 2136 KB Output is correct
37 Correct 35 ms 2140 KB Output is correct
38 Correct 59 ms 2140 KB Output is correct
39 Correct 45 ms 2608 KB Output is correct
40 Correct 44 ms 2612 KB Output is correct
41 Correct 77 ms 2396 KB Output is correct
42 Correct 61 ms 3312 KB Output is correct
43 Correct 57 ms 3288 KB Output is correct
44 Correct 109 ms 3160 KB Output is correct
45 Correct 76 ms 3804 KB Output is correct
46 Correct 67 ms 3812 KB Output is correct
47 Correct 119 ms 3676 KB Output is correct
48 Correct 80 ms 4404 KB Output is correct
49 Correct 88 ms 4424 KB Output is correct
50 Correct 133 ms 4188 KB Output is correct
51 Correct 108 ms 5004 KB Output is correct
52 Correct 87 ms 5008 KB Output is correct
53 Correct 181 ms 5200 KB Output is correct
54 Correct 119 ms 5692 KB Output is correct
55 Correct 112 ms 5672 KB Output is correct
56 Correct 217 ms 5468 KB Output is correct
57 Correct 141 ms 6388 KB Output is correct
58 Correct 116 ms 6408 KB Output is correct
59 Correct 249 ms 6232 KB Output is correct
60 Correct 144 ms 7188 KB Output is correct
61 Correct 139 ms 7184 KB Output is correct
62 Correct 249 ms 7004 KB Output is correct
63 Correct 384 ms 7000 KB Output is correct
64 Correct 412 ms 7004 KB Output is correct
65 Correct 385 ms 7116 KB Output is correct
66 Correct 379 ms 7344 KB Output is correct
67 Correct 335 ms 7004 KB Output is correct
68 Correct 327 ms 7252 KB Output is correct
69 Correct 351 ms 7000 KB Output is correct
70 Correct 315 ms 7004 KB Output is correct
71 Correct 347 ms 7004 KB Output is correct
72 Correct 316 ms 7180 KB Output is correct
73 Correct 313 ms 7260 KB Output is correct
74 Correct 301 ms 7452 KB Output is correct
75 Correct 351 ms 7392 KB Output is correct
76 Correct 324 ms 7456 KB Output is correct
77 Correct 331 ms 7432 KB Output is correct
78 Correct 332 ms 7416 KB Output is correct
79 Correct 287 ms 7416 KB Output is correct
80 Correct 307 ms 7404 KB Output is correct
81 Correct 304 ms 7260 KB Output is correct
82 Correct 321 ms 7508 KB Output is correct
83 Correct 322 ms 7256 KB Output is correct
84 Correct 346 ms 7380 KB Output is correct
85 Correct 329 ms 7376 KB Output is correct
86 Correct 330 ms 7516 KB Output is correct
87 Correct 311 ms 7384 KB Output is correct
88 Correct 330 ms 7256 KB Output is correct
89 Correct 318 ms 7316 KB Output is correct
90 Correct 319 ms 7260 KB Output is correct
91 Correct 350 ms 7256 KB Output is correct
92 Correct 346 ms 7320 KB Output is correct