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Submission #978625

# Submission time Handle Problem Language Result Execution time Memory
978625 2024-05-09T11:49:13 Z Bodisha Mecho (IOI09_mecho) C++17
100 / 100
 538 ms 7212 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:136:23: warning: 'mechox' may be used uninitialized in this function [-Wmaybe-uninitialized]
  136 |   mecho_visited[mechox][mechoy] = true;
      |                       ^
mecho.cpp:192:29: warning: 'home_y' may be used uninitialized in this function [-Wmaybe-uninitialized]
  192 |    int nx = home_x + dx[i], ny = home_y + dy[i];
      |                             ^~
mecho.cpp:192:8: warning: 'home_x' may be used uninitialized in this function [-Wmaybe-uninitialized]
  192 |    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 0 ms 344 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 432 ms 6652 KB Output is correct
8 Correct 0 ms 348 KB Output is correct
9 Correct 0 ms 348 KB Output is correct
10 Correct 1 ms 348 KB Output is correct
11 Correct 0 ms 600 KB Output is correct
12 Correct 1 ms 348 KB Output is correct
13 Correct 2 ms 348 KB Output is correct
14 Correct 2 ms 508 KB Output is correct
15 Correct 0 ms 348 KB Output is correct
16 Correct 1 ms 344 KB Output is correct
17 Correct 0 ms 348 KB Output is correct
18 Correct 1 ms 348 KB Output is correct
19 Correct 0 ms 348 KB Output is correct
20 Correct 0 ms 348 KB Output is correct
21 Correct 1 ms 348 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 2 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 344 KB Output is correct
32 Correct 2 ms 348 KB Output is correct
33 Correct 32 ms 1732 KB Output is correct
34 Correct 33 ms 1724 KB Output is correct
35 Correct 62 ms 1660 KB Output is correct
36 Correct 45 ms 2004 KB Output is correct
37 Correct 41 ms 2008 KB Output is correct
38 Correct 78 ms 2020 KB Output is correct
39 Correct 52 ms 2400 KB Output is correct
40 Correct 56 ms 2404 KB Output is correct
41 Correct 108 ms 2392 KB Output is correct
42 Correct 68 ms 3060 KB Output is correct
43 Correct 66 ms 3056 KB Output is correct
44 Correct 131 ms 2908 KB Output is correct
45 Correct 100 ms 3676 KB Output is correct
46 Correct 77 ms 3528 KB Output is correct
47 Correct 158 ms 3500 KB Output is correct
48 Correct 97 ms 4052 KB Output is correct
49 Correct 100 ms 4436 KB Output is correct
50 Correct 186 ms 3932 KB Output is correct
51 Correct 122 ms 4588 KB Output is correct
52 Correct 114 ms 4584 KB Output is correct
53 Correct 243 ms 4588 KB Output is correct
54 Correct 140 ms 5204 KB Output is correct
55 Correct 164 ms 5204 KB Output is correct
56 Correct 309 ms 5188 KB Output is correct
57 Correct 162 ms 5860 KB Output is correct
58 Correct 165 ms 5876 KB Output is correct
59 Correct 341 ms 5836 KB Output is correct
60 Correct 213 ms 6540 KB Output is correct
61 Correct 171 ms 6532 KB Output is correct
62 Correct 426 ms 6492 KB Output is correct
63 Correct 422 ms 6744 KB Output is correct
64 Correct 538 ms 6524 KB Output is correct
65 Correct 483 ms 7212 KB Output is correct
66 Correct 475 ms 6828 KB Output is correct
67 Correct 434 ms 6488 KB Output is correct
68 Correct 397 ms 6548 KB Output is correct
69 Correct 407 ms 6492 KB Output is correct
70 Correct 416 ms 6800 KB Output is correct
71 Correct 398 ms 6492 KB Output is correct
72 Correct 378 ms 6564 KB Output is correct
73 Correct 376 ms 6616 KB Output is correct
74 Correct 401 ms 6744 KB Output is correct
75 Correct 428 ms 6816 KB Output is correct
76 Correct 402 ms 6744 KB Output is correct
77 Correct 432 ms 6816 KB Output is correct
78 Correct 404 ms 6780 KB Output is correct
79 Correct 377 ms 6748 KB Output is correct
80 Correct 379 ms 6784 KB Output is correct
81 Correct 419 ms 6872 KB Output is correct
82 Correct 398 ms 6996 KB Output is correct
83 Correct 425 ms 6836 KB Output is correct
84 Correct 418 ms 6748 KB Output is correct
85 Correct 451 ms 6768 KB Output is correct
86 Correct 419 ms 6744 KB Output is correct
87 Correct 420 ms 6748 KB Output is correct
88 Correct 468 ms 6692 KB Output is correct
89 Correct 410 ms 6688 KB Output is correct
90 Correct 413 ms 6492 KB Output is correct
91 Correct 477 ms 6688 KB Output is correct
92 Correct 447 ms 6692 KB Output is correct