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답안 #944913

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
944913 2024-03-13T07:58:15 Z artixkrishna Mecho (IOI09_mecho) C++14
100 / 100
 557 ms 7660 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

# 결과 실행 시간 메모리 Grader output
1 Correct 1 ms 344 KB Output is correct
2 Correct 1 ms 604 KB Output is correct
3 Correct 0 ms 348 KB Output is correct
4 Correct 1 ms 348 KB Output is correct
5 Correct 0 ms 348 KB Output is correct
6 Correct 0 ms 604 KB Output is correct
7 Correct 458 ms 6684 KB Output is correct
8 Correct 1 ms 344 KB Output is correct
9 Correct 1 ms 348 KB Output is correct
10 Correct 1 ms 460 KB Output is correct
11 Correct 0 ms 344 KB Output is correct
12 Correct 1 ms 348 KB Output is correct
13 Correct 2 ms 600 KB Output is correct
14 Correct 2 ms 452 KB Output is correct
15 Correct 1 ms 344 KB Output is correct
16 Correct 1 ms 348 KB Output is correct
17 Correct 1 ms 812 KB Output is correct
18 Correct 1 ms 348 KB Output is correct
19 Correct 1 ms 460 KB Output is correct
20 Correct 1 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 604 KB Output is correct
26 Correct 1 ms 348 KB Output is correct
27 Correct 1 ms 344 KB Output is correct
28 Correct 2 ms 348 KB Output is correct
29 Correct 1 ms 348 KB Output is correct
30 Correct 2 ms 604 KB Output is correct
31 Correct 2 ms 348 KB Output is correct
32 Correct 2 ms 348 KB Output is correct
33 Correct 39 ms 1804 KB Output is correct
34 Correct 44 ms 1816 KB Output is correct
35 Correct 67 ms 1628 KB Output is correct
36 Correct 43 ms 2132 KB Output is correct
37 Correct 58 ms 2260 KB Output is correct
38 Correct 79 ms 2088 KB Output is correct
39 Correct 60 ms 2660 KB Output is correct
40 Correct 56 ms 2536 KB Output is correct
41 Correct 124 ms 2536 KB Output is correct
42 Correct 71 ms 3240 KB Output is correct
43 Correct 72 ms 3248 KB Output is correct
44 Correct 141 ms 3164 KB Output is correct
45 Correct 92 ms 3708 KB Output is correct
46 Correct 94 ms 3732 KB Output is correct
47 Correct 170 ms 3728 KB Output is correct
48 Correct 121 ms 4280 KB Output is correct
49 Correct 112 ms 4284 KB Output is correct
50 Correct 213 ms 4592 KB Output is correct
51 Correct 137 ms 5232 KB Output is correct
52 Correct 126 ms 4880 KB Output is correct
53 Correct 267 ms 4908 KB Output is correct
54 Correct 175 ms 5484 KB Output is correct
55 Correct 166 ms 5608 KB Output is correct
56 Correct 299 ms 5720 KB Output is correct
57 Correct 173 ms 6168 KB Output is correct
58 Correct 172 ms 6224 KB Output is correct
59 Correct 337 ms 6192 KB Output is correct
60 Correct 216 ms 7044 KB Output is correct
61 Correct 187 ms 7660 KB Output is correct
62 Correct 354 ms 6932 KB Output is correct
63 Correct 443 ms 6916 KB Output is correct
64 Correct 557 ms 6892 KB Output is correct
65 Correct 494 ms 7056 KB Output is correct
66 Correct 513 ms 6920 KB Output is correct
67 Correct 437 ms 7000 KB Output is correct
68 Correct 413 ms 7396 KB Output is correct
69 Correct 415 ms 6744 KB Output is correct
70 Correct 412 ms 6908 KB Output is correct
71 Correct 460 ms 6800 KB Output is correct
72 Correct 385 ms 6972 KB Output is correct
73 Correct 390 ms 7508 KB Output is correct
74 Correct 429 ms 7224 KB Output is correct
75 Correct 476 ms 7276 KB Output is correct
76 Correct 424 ms 7212 KB Output is correct
77 Correct 428 ms 7260 KB Output is correct
78 Correct 427 ms 6948 KB Output is correct
79 Correct 409 ms 7168 KB Output is correct
80 Correct 395 ms 7148 KB Output is correct
81 Correct 392 ms 7172 KB Output is correct
82 Correct 394 ms 7248 KB Output is correct
83 Correct 418 ms 7164 KB Output is correct
84 Correct 410 ms 7252 KB Output is correct
85 Correct 433 ms 7128 KB Output is correct
86 Correct 410 ms 7000 KB Output is correct
87 Correct 411 ms 7248 KB Output is correct
88 Correct 403 ms 7124 KB Output is correct
89 Correct 422 ms 7080 KB Output is correct
90 Correct 407 ms 7004 KB Output is correct
91 Correct 429 ms 7100 KB Output is correct
92 Correct 449 ms 7128 KB Output is correct