답안 #529633

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
529633	2022-02-23T09:34:08 Z	thezomb1e	Mecho (IOI09_mecho)	C++17	100 / 100	635 ms	6852 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:77:23: 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	1 ms	204 KB	Output is correct
2	Correct	1 ms	204 KB	Output is correct
3	Correct	1 ms	204 KB	Output is correct
4	Correct	1 ms	204 KB	Output is correct
5	Correct	0 ms	204 KB	Output is correct
6	Correct	0 ms	204 KB	Output is correct
7	Correct	531 ms	6488 KB	Output is correct
8	Correct	1 ms	204 KB	Output is correct
9	Correct	0 ms	204 KB	Output is correct
10	Correct	1 ms	204 KB	Output is correct
11	Correct	0 ms	204 KB	Output is correct
12	Correct	2 ms	332 KB	Output is correct
13	Correct	2 ms	332 KB	Output is correct
14	Correct	2 ms	332 KB	Output is correct
15	Correct	1 ms	204 KB	Output is correct
16	Correct	1 ms	332 KB	Output is correct
17	Correct	1 ms	332 KB	Output is correct
18	Correct	1 ms	204 KB	Output is correct
19	Correct	1 ms	332 KB	Output is correct
20	Correct	1 ms	332 KB	Output is correct
21	Correct	1 ms	332 KB	Output is correct
22	Correct	1 ms	332 KB	Output is correct
23	Correct	1 ms	332 KB	Output is correct
24	Correct	1 ms	332 KB	Output is correct
25	Correct	1 ms	332 KB	Output is correct
26	Correct	2 ms	332 KB	Output is correct
27	Correct	1 ms	332 KB	Output is correct
28	Correct	2 ms	332 KB	Output is correct
29	Correct	2 ms	332 KB	Output is correct
30	Correct	2 ms	332 KB	Output is correct
31	Correct	2 ms	332 KB	Output is correct
32	Correct	2 ms	332 KB	Output is correct
33	Correct	40 ms	1516 KB	Output is correct
34	Correct	40 ms	1532 KB	Output is correct
35	Correct	77 ms	1612 KB	Output is correct
36	Correct	53 ms	1996 KB	Output is correct
37	Correct	52 ms	1872 KB	Output is correct
38	Correct	95 ms	1868 KB	Output is correct
39	Correct	64 ms	2252 KB	Output is correct
40	Correct	67 ms	2232 KB	Output is correct
41	Correct	127 ms	2144 KB	Output is correct
42	Correct	93 ms	3052 KB	Output is correct
43	Correct	122 ms	2912 KB	Output is correct
44	Correct	162 ms	2896 KB	Output is correct
45	Correct	106 ms	3404 KB	Output is correct
46	Correct	102 ms	3420 KB	Output is correct
47	Correct	208 ms	3356 KB	Output is correct
48	Correct	118 ms	3932 KB	Output is correct
49	Correct	125 ms	3920 KB	Output is correct
50	Correct	281 ms	3996 KB	Output is correct
51	Correct	145 ms	4444 KB	Output is correct
52	Correct	144 ms	4476 KB	Output is correct
53	Correct	291 ms	4428 KB	Output is correct
54	Correct	215 ms	5060 KB	Output is correct
55	Correct	170 ms	5064 KB	Output is correct
56	Correct	395 ms	5048 KB	Output is correct
57	Correct	202 ms	5716 KB	Output is correct
58	Correct	209 ms	5692 KB	Output is correct
59	Correct	421 ms	5764 KB	Output is correct
60	Correct	243 ms	6388 KB	Output is correct
61	Correct	227 ms	6484 KB	Output is correct
62	Correct	430 ms	6380 KB	Output is correct
63	Correct	514 ms	6380 KB	Output is correct
64	Correct	635 ms	6384 KB	Output is correct
65	Correct	566 ms	6380 KB	Output is correct
66	Correct	562 ms	6436 KB	Output is correct
67	Correct	509 ms	6384 KB	Output is correct
68	Correct	511 ms	6408 KB	Output is correct
69	Correct	495 ms	6600 KB	Output is correct
70	Correct	498 ms	6416 KB	Output is correct
71	Correct	479 ms	6424 KB	Output is correct
72	Correct	446 ms	6468 KB	Output is correct
73	Correct	466 ms	6680 KB	Output is correct
74	Correct	509 ms	6688 KB	Output is correct
75	Correct	545 ms	6792 KB	Output is correct
76	Correct	531 ms	6852 KB	Output is correct
77	Correct	569 ms	6808 KB	Output is correct
78	Correct	490 ms	6604 KB	Output is correct
79	Correct	457 ms	6732 KB	Output is correct
80	Correct	467 ms	6640 KB	Output is correct
81	Correct	472 ms	6640 KB	Output is correct
82	Correct	505 ms	6644 KB	Output is correct
83	Correct	523 ms	6604 KB	Output is correct
84	Correct	502 ms	6676 KB	Output is correct
85	Correct	532 ms	6724 KB	Output is correct
86	Correct	499 ms	6604 KB	Output is correct
87	Correct	517 ms	6604 KB	Output is correct
88	Correct	562 ms	6548 KB	Output is correct
89	Correct	509 ms	6484 KB	Output is correct
90	Correct	520 ms	6544 KB	Output is correct
91	Correct	510 ms	6552 KB	Output is correct
92	Correct	545 ms	6596 KB	Output is correct