답안 #599849

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
599849	2022-07-20T02:13:27 Z	alexz1205	Mecho (IOI09_mecho)	C++14	100 / 100	637 ms	6748 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:77:31: warning: 'mechoy' may be used uninitialized in this function [-Wmaybe-uninitialized]
   77 |   mecho_visited[mechox][mechoy] = true;
      |                               ^
mecho.cpp:77:23: warning: 'mechox' may be used uninitialized in this function [-Wmaybe-uninitialized]
   77 |   mecho_visited[mechox][mechoy] = true;
      |                       ^
mecho.cpp:109:29: warning: 'home_y' may be used uninitialized in this function [-Wmaybe-uninitialized]
  109 |    int nx = home_x + dx[i], ny = home_y + dy[i];
      |                             ^~
mecho.cpp:109:8: warning: 'home_x' may be used uninitialized in this function [-Wmaybe-uninitialized]
  109 |    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	212 KB	Output is correct
2	Correct	0 ms	212 KB	Output is correct
3	Correct	1 ms	212 KB	Output is correct
4	Correct	0 ms	212 KB	Output is correct
5	Correct	0 ms	212 KB	Output is correct
6	Correct	0 ms	212 KB	Output is correct
7	Correct	570 ms	6500 KB	Output is correct
8	Correct	1 ms	212 KB	Output is correct
9	Correct	0 ms	212 KB	Output is correct
10	Correct	1 ms	212 KB	Output is correct
11	Correct	1 ms	212 KB	Output is correct
12	Correct	2 ms	340 KB	Output is correct
13	Correct	2 ms	340 KB	Output is correct
14	Correct	2 ms	340 KB	Output is correct
15	Correct	1 ms	340 KB	Output is correct
16	Correct	0 ms	212 KB	Output is correct
17	Correct	1 ms	212 KB	Output is correct
18	Correct	1 ms	212 KB	Output is correct
19	Correct	1 ms	212 KB	Output is correct
20	Correct	1 ms	340 KB	Output is correct
21	Correct	2 ms	340 KB	Output is correct
22	Correct	1 ms	340 KB	Output is correct
23	Correct	1 ms	340 KB	Output is correct
24	Correct	1 ms	340 KB	Output is correct
25	Correct	2 ms	340 KB	Output is correct
26	Correct	1 ms	364 KB	Output is correct
27	Correct	1 ms	340 KB	Output is correct
28	Correct	2 ms	340 KB	Output is correct
29	Correct	2 ms	340 KB	Output is correct
30	Correct	2 ms	340 KB	Output is correct
31	Correct	2 ms	340 KB	Output is correct
32	Correct	2 ms	340 KB	Output is correct
33	Correct	43 ms	1588 KB	Output is correct
34	Correct	43 ms	1536 KB	Output is correct
35	Correct	76 ms	1532 KB	Output is correct
36	Correct	54 ms	1988 KB	Output is correct
37	Correct	53 ms	1888 KB	Output is correct
38	Correct	100 ms	1876 KB	Output is correct
39	Correct	62 ms	2268 KB	Output is correct
40	Correct	72 ms	2400 KB	Output is correct
41	Correct	134 ms	2248 KB	Output is correct
42	Correct	90 ms	3156 KB	Output is correct
43	Correct	89 ms	3012 KB	Output is correct
44	Correct	205 ms	2900 KB	Output is correct
45	Correct	111 ms	3380 KB	Output is correct
46	Correct	100 ms	3380 KB	Output is correct
47	Correct	186 ms	3372 KB	Output is correct
48	Correct	128 ms	3908 KB	Output is correct
49	Correct	128 ms	3916 KB	Output is correct
50	Correct	241 ms	3916 KB	Output is correct
51	Correct	176 ms	4468 KB	Output is correct
52	Correct	157 ms	4516 KB	Output is correct
53	Correct	282 ms	4456 KB	Output is correct
54	Correct	192 ms	5072 KB	Output is correct
55	Correct	185 ms	5068 KB	Output is correct
56	Correct	343 ms	5076 KB	Output is correct
57	Correct	209 ms	5696 KB	Output is correct
58	Correct	189 ms	5716 KB	Output is correct
59	Correct	430 ms	5616 KB	Output is correct
60	Correct	233 ms	6404 KB	Output is correct
61	Correct	222 ms	6384 KB	Output is correct
62	Correct	495 ms	6348 KB	Output is correct
63	Correct	502 ms	6392 KB	Output is correct
64	Correct	637 ms	6392 KB	Output is correct
65	Correct	568 ms	6412 KB	Output is correct
66	Correct	580 ms	6428 KB	Output is correct
67	Correct	504 ms	6392 KB	Output is correct
68	Correct	485 ms	6416 KB	Output is correct
69	Correct	499 ms	6416 KB	Output is correct
70	Correct	454 ms	6476 KB	Output is correct
71	Correct	477 ms	6548 KB	Output is correct
72	Correct	449 ms	6416 KB	Output is correct
73	Correct	507 ms	6732 KB	Output is correct
74	Correct	508 ms	6688 KB	Output is correct
75	Correct	580 ms	6748 KB	Output is correct
76	Correct	564 ms	6688 KB	Output is correct
77	Correct	512 ms	6688 KB	Output is correct
78	Correct	502 ms	6656 KB	Output is correct
79	Correct	477 ms	6696 KB	Output is correct
80	Correct	482 ms	6652 KB	Output is correct
81	Correct	494 ms	6648 KB	Output is correct
82	Correct	494 ms	6704 KB	Output is correct
83	Correct	538 ms	6500 KB	Output is correct
84	Correct	518 ms	6612 KB	Output is correct
85	Correct	525 ms	6612 KB	Output is correct
86	Correct	556 ms	6736 KB	Output is correct
87	Correct	512 ms	6616 KB	Output is correct
88	Correct	515 ms	6576 KB	Output is correct
89	Correct	533 ms	6548 KB	Output is correct
90	Correct	524 ms	6560 KB	Output is correct
91	Correct	545 ms	6604 KB	Output is correct
92	Correct	594 ms	6680 KB	Output is correct