Submission #605577

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
605577	2022-07-25T18:58:16 Z	tonfai_nokhong	Mecho (IOI09_mecho)	C++17	100 / 100	643 ms	7448 KB

mecho

//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;
	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;

		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;
				}
			}
		}
		
		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];
				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;
				}
			}
		}
       
		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:74:23: warning: 'mechox' may be used uninitialized in this function [-Wmaybe-uninitialized]
   74 |   mecho_visited[mechox][mechoy] = true;
      |                       ^
mecho.cpp:96:29: warning: 'home_y' may be used uninitialized in this function [-Wmaybe-uninitialized]
   96 |    int nx = home_x + dx[i], ny = home_y + dy[i];
      |                             ^~
mecho.cpp:96:8: warning: 'home_x' may be used uninitialized in this function [-Wmaybe-uninitialized]
   96 |    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	212 KB	Output is correct
2	Correct	1 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	1 ms	212 KB	Output is correct
6	Correct	0 ms	320 KB	Output is correct
7	Correct	542 ms	7128 KB	Output is correct
8	Correct	1 ms	324 KB	Output is correct
9	Correct	1 ms	320 KB	Output is correct
10	Correct	1 ms	212 KB	Output is correct
11	Correct	1 ms	324 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	340 KB	Output is correct
18	Correct	1 ms	340 KB	Output is correct
19	Correct	1 ms	340 KB	Output is correct
20	Correct	1 ms	340 KB	Output is correct
21	Correct	1 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	3 ms	340 KB	Output is correct
26	Correct	2 ms	340 KB	Output is correct
27	Correct	2 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	40 ms	1696 KB	Output is correct
34	Correct	39 ms	1684 KB	Output is correct
35	Correct	77 ms	1652 KB	Output is correct
36	Correct	50 ms	2048 KB	Output is correct
37	Correct	53 ms	2064 KB	Output is correct
38	Correct	101 ms	2032 KB	Output is correct
39	Correct	63 ms	2444 KB	Output is correct
40	Correct	65 ms	2456 KB	Output is correct
41	Correct	131 ms	2388 KB	Output is correct
42	Correct	90 ms	3164 KB	Output is correct
43	Correct	83 ms	3176 KB	Output is correct
44	Correct	165 ms	3168 KB	Output is correct
45	Correct	104 ms	3680 KB	Output is correct
46	Correct	101 ms	3684 KB	Output is correct
47	Correct	198 ms	3792 KB	Output is correct
48	Correct	118 ms	4276 KB	Output is correct
49	Correct	124 ms	4300 KB	Output is correct
50	Correct	238 ms	4260 KB	Output is correct
51	Correct	149 ms	4908 KB	Output is correct
52	Correct	144 ms	4872 KB	Output is correct
53	Correct	306 ms	4864 KB	Output is correct
54	Correct	176 ms	5548 KB	Output is correct
55	Correct	174 ms	5564 KB	Output is correct
56	Correct	422 ms	5540 KB	Output is correct
57	Correct	195 ms	6276 KB	Output is correct
58	Correct	204 ms	6384 KB	Output is correct
59	Correct	385 ms	6228 KB	Output is correct
60	Correct	241 ms	7036 KB	Output is correct
61	Correct	224 ms	7164 KB	Output is correct
62	Correct	438 ms	7000 KB	Output is correct
63	Correct	508 ms	6980 KB	Output is correct
64	Correct	643 ms	7028 KB	Output is correct
65	Correct	586 ms	7016 KB	Output is correct
66	Correct	560 ms	7088 KB	Output is correct
67	Correct	540 ms	7148 KB	Output is correct
68	Correct	453 ms	7048 KB	Output is correct
69	Correct	499 ms	7116 KB	Output is correct
70	Correct	454 ms	7100 KB	Output is correct
71	Correct	479 ms	7044 KB	Output is correct
72	Correct	488 ms	7052 KB	Output is correct
73	Correct	452 ms	7320 KB	Output is correct
74	Correct	502 ms	7448 KB	Output is correct
75	Correct	559 ms	7320 KB	Output is correct
76	Correct	507 ms	7244 KB	Output is correct
77	Correct	538 ms	7444 KB	Output is correct
78	Correct	491 ms	7292 KB	Output is correct
79	Correct	480 ms	7288 KB	Output is correct
80	Correct	502 ms	7352 KB	Output is correct
81	Correct	476 ms	7284 KB	Output is correct
82	Correct	483 ms	7280 KB	Output is correct
83	Correct	544 ms	7236 KB	Output is correct
84	Correct	516 ms	7380 KB	Output is correct
85	Correct	538 ms	7252 KB	Output is correct
86	Correct	527 ms	7244 KB	Output is correct
87	Correct	525 ms	7368 KB	Output is correct
88	Correct	518 ms	7184 KB	Output is correct
89	Correct	515 ms	7184 KB	Output is correct
90	Correct	526 ms	7188 KB	Output is correct
91	Correct	528 ms	7188 KB	Output is correct
92	Correct	548 ms	7184 KB	Output is correct