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Submission #930741

# Submission time Handle Problem Language Result Execution time Memory
930741 2024-02-20T11:01:22 Z Amaarsaa Mecho (IOI09_mecho) C++14
100 / 100
 524 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 1 ms 344 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 0 ms 348 KB Output is correct
5 Correct 0 ms 344 KB Output is correct
6 Correct 1 ms 348 KB Output is correct
7 Correct 419 ms 6672 KB Output is correct
8 Correct 1 ms 344 KB Output is correct
9 Correct 1 ms 344 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 348 KB Output is correct
14 Correct 2 ms 348 KB Output is correct
15 Correct 1 ms 460 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 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 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 464 KB Output is correct
29 Correct 1 ms 348 KB Output is correct
30 Correct 1 ms 468 KB Output is correct
31 Correct 2 ms 348 KB Output is correct
32 Correct 1 ms 348 KB Output is correct
33 Correct 34 ms 1692 KB Output is correct
34 Correct 33 ms 1728 KB Output is correct
35 Correct 61 ms 1628 KB Output is correct
36 Correct 43 ms 2096 KB Output is correct
37 Correct 46 ms 2128 KB Output is correct
38 Correct 78 ms 1880 KB Output is correct
39 Correct 58 ms 2708 KB Output is correct
40 Correct 52 ms 2544 KB Output is correct
41 Correct 108 ms 2544 KB Output is correct
42 Correct 69 ms 3196 KB Output is correct
43 Correct 64 ms 3216 KB Output is correct
44 Correct 165 ms 3220 KB Output is correct
45 Correct 86 ms 3692 KB Output is correct
46 Correct 77 ms 3972 KB Output is correct
47 Correct 159 ms 3672 KB Output is correct
48 Correct 103 ms 4276 KB Output is correct
49 Correct 98 ms 4452 KB Output is correct
50 Correct 202 ms 4184 KB Output is correct
51 Correct 129 ms 5228 KB Output is correct
52 Correct 113 ms 5064 KB Output is correct
53 Correct 234 ms 4896 KB Output is correct
54 Correct 154 ms 5636 KB Output is correct
55 Correct 132 ms 5540 KB Output is correct
56 Correct 306 ms 5244 KB Output is correct
57 Correct 174 ms 6280 KB Output is correct
58 Correct 151 ms 6200 KB Output is correct
59 Correct 326 ms 5968 KB Output is correct
60 Correct 200 ms 7096 KB Output is correct
61 Correct 172 ms 6928 KB Output is correct
62 Correct 367 ms 6920 KB Output is correct
63 Correct 421 ms 6736 KB Output is correct
64 Correct 524 ms 6880 KB Output is correct
65 Correct 478 ms 6952 KB Output is correct
66 Correct 456 ms 7004 KB Output is correct
67 Correct 430 ms 6920 KB Output is correct
68 Correct 391 ms 6736 KB Output is correct
69 Correct 412 ms 6736 KB Output is correct
70 Correct 387 ms 6960 KB Output is correct
71 Correct 410 ms 6748 KB Output is correct
72 Correct 378 ms 6748 KB Output is correct
73 Correct 378 ms 7220 KB Output is correct
74 Correct 401 ms 7216 KB Output is correct
75 Correct 449 ms 7516 KB Output is correct
76 Correct 407 ms 7200 KB Output is correct
77 Correct 402 ms 7176 KB Output is correct
78 Correct 422 ms 7192 KB Output is correct
79 Correct 378 ms 7216 KB Output is correct
80 Correct 387 ms 7380 KB Output is correct
81 Correct 434 ms 7152 KB Output is correct
82 Correct 388 ms 6992 KB Output is correct
83 Correct 414 ms 6996 KB Output is correct
84 Correct 414 ms 7004 KB Output is correct
85 Correct 436 ms 6948 KB Output is correct
86 Correct 430 ms 7164 KB Output is correct
87 Correct 415 ms 7168 KB Output is correct
88 Correct 414 ms 6992 KB Output is correct
89 Correct 424 ms 7068 KB Output is correct
90 Correct 416 ms 7112 KB Output is correct
91 Correct 442 ms 7088 KB Output is correct
92 Correct 449 ms 7124 KB Output is correct