답안 #895626

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
895626	2023-12-30T12:04:07 Z	lmkae	Mecho (IOI09_mecho)	C++14	100 / 100	520 ms	7016 KB

mecho

#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	0 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	348 KB	Output is correct
6	Correct	0 ms	348 KB	Output is correct
7	Correct	442 ms	6652 KB	Output is correct
8	Correct	1 ms	344 KB	Output is correct
9	Correct	0 ms	344 KB	Output is correct
10	Correct	0 ms	348 KB	Output is correct
11	Correct	1 ms	348 KB	Output is correct
12	Correct	1 ms	348 KB	Output is correct
13	Correct	1 ms	344 KB	Output is correct
14	Correct	2 ms	348 KB	Output is correct
15	Correct	0 ms	348 KB	Output is correct
16	Correct	1 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	1 ms	344 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	348 KB	Output is correct
26	Correct	1 ms	344 KB	Output is correct
27	Correct	1 ms	348 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	348 KB	Output is correct
31	Correct	1 ms	348 KB	Output is correct
32	Correct	1 ms	348 KB	Output is correct
33	Correct	32 ms	1680 KB	Output is correct
34	Correct	31 ms	1732 KB	Output is correct
35	Correct	61 ms	1624 KB	Output is correct
36	Correct	44 ms	2004 KB	Output is correct
37	Correct	40 ms	1924 KB	Output is correct
38	Correct	81 ms	1880 KB	Output is correct
39	Correct	60 ms	2848 KB	Output is correct
40	Correct	52 ms	2420 KB	Output is correct
41	Correct	107 ms	2392 KB	Output is correct
42	Correct	68 ms	3052 KB	Output is correct
43	Correct	69 ms	3040 KB	Output is correct
44	Correct	144 ms	3156 KB	Output is correct
45	Correct	92 ms	3524 KB	Output is correct
46	Correct	77 ms	3512 KB	Output is correct
47	Correct	160 ms	3504 KB	Output is correct
48	Correct	101 ms	4040 KB	Output is correct
49	Correct	114 ms	4052 KB	Output is correct
50	Correct	188 ms	3928 KB	Output is correct
51	Correct	122 ms	4600 KB	Output is correct
52	Correct	120 ms	4880 KB	Output is correct
53	Correct	247 ms	4584 KB	Output is correct
54	Correct	175 ms	5196 KB	Output is correct
55	Correct	134 ms	5200 KB	Output is correct
56	Correct	280 ms	4956 KB	Output is correct
57	Correct	188 ms	5860 KB	Output is correct
58	Correct	157 ms	6004 KB	Output is correct
59	Correct	332 ms	5836 KB	Output is correct
60	Correct	193 ms	6536 KB	Output is correct
61	Correct	184 ms	6500 KB	Output is correct
62	Correct	364 ms	6488 KB	Output is correct
63	Correct	447 ms	6524 KB	Output is correct
64	Correct	520 ms	6520 KB	Output is correct
65	Correct	478 ms	6524 KB	Output is correct
66	Correct	499 ms	6532 KB	Output is correct
67	Correct	427 ms	6528 KB	Output is correct
68	Correct	411 ms	6572 KB	Output is correct
69	Correct	434 ms	6492 KB	Output is correct
70	Correct	380 ms	6568 KB	Output is correct
71	Correct	407 ms	6556 KB	Output is correct
72	Correct	390 ms	6488 KB	Output is correct
73	Correct	378 ms	6744 KB	Output is correct
74	Correct	405 ms	6728 KB	Output is correct
75	Correct	452 ms	7016 KB	Output is correct
76	Correct	399 ms	6840 KB	Output is correct
77	Correct	420 ms	6816 KB	Output is correct
78	Correct	416 ms	7000 KB	Output is correct
79	Correct	383 ms	6788 KB	Output is correct
80	Correct	403 ms	6784 KB	Output is correct
81	Correct	409 ms	6748 KB	Output is correct
82	Correct	383 ms	6748 KB	Output is correct
83	Correct	404 ms	6748 KB	Output is correct
84	Correct	433 ms	6740 KB	Output is correct
85	Correct	433 ms	6748 KB	Output is correct
86	Correct	419 ms	6996 KB	Output is correct
87	Correct	437 ms	6752 KB	Output is correct
88	Correct	434 ms	6740 KB	Output is correct
89	Correct	439 ms	6688 KB	Output is correct
90	Correct	448 ms	6688 KB	Output is correct
91	Correct	460 ms	6688 KB	Output is correct
92	Correct	482 ms	6688 KB	Output is correct