Submission #621403

# Submission time Handle Problem Language Result Execution time Memory
621403 2022-08-03T18:31:05 Z abcisosm5 Mecho (IOI09_mecho) C++17
84 / 100
801 ms 2876 KB
#include <bits/stdc++.h>
using namespace std;
#define pi pair<int, int>
#define f first
#define s second

int N, S;
const int MN = 800;
char grid[MN][MN] = {{}};
vector<pi> hives;
pi M; pi D;
int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};

void movebees(queue<pi> (&b), char (&v)[MN][MN], int t){
	for(int i = 0; i < t; i++){
		queue<pi> nextb;
		while(!b.empty()){
			pi p = b.front(); b.pop();
			for(int d = 0; d < 4; d++){
				int nx = p.f + dx[d]; int ny = p.s + dy[d];
				if(nx < 0 || nx >= N || ny < 0 || ny >= N) continue;
				if(v[nx][ny] != 'B' && grid[nx][ny] == 'G'){
					v[nx][ny] = 'B';
					nextb.push({nx, ny});
				}
			}
		}
		b = nextb;
	}
}

bool movemecho(queue<pi> (&m), char (&v)[MN][MN]){
	for(int i = 0; i < S; i++){
		queue<pi> nextm;
		while(!m.empty()){
			pi p = m.front(); m.pop();
			if(v[p.f][p.s] == 'B') continue; //invalidate positions that are now occupied by bees
			for(int d = 0; d < 4; d++){
				int nx = p.f + dx[d]; int ny = p.s + dy[d];
				if(nx < 0 || nx >= N || ny < 0 || ny >= N) continue;
				if(!v[nx][ny] && grid[nx][ny] != 'T'){
					v[nx][ny] = 'M';
					if(grid[nx][ny] == 'D') return true;
					nextm.push({nx, ny});
				}
			}
		}
		m = nextm;
	}
	return false;
}

bool works(int t){ //O(N^2)
	char visited[MN][MN] = {{}};
	queue<pi> bees;
	for(pi p : hives){
		bees.push(p);
		visited[p.first][p.second] = 'B'; 
	}
	movebees(bees, visited, t);

	queue<pi> mecho; mecho.push(M); visited[M.f][M.s] = 'M';
	
	for(int i = 0; i < N*N/2; i++){
		//first, move mecho S steps
		if(mecho.empty()) break;
		bool success = movemecho(mecho, visited);
		if(success) return true;

		//then, move bees 1 step
		movebees(bees, visited, 1);
	}

	return false;
}

int main(){
	cin.tie(0)->sync_with_stdio(0);

	cin >> N >> S;

	for(int i = 0; i < N; i++){
		for(int j = 0; j < N; j++){
			cin >> grid[i][j];

			if(grid[i][j] == 'M') M = {i, j};
			if(grid[i][j] == 'D') D = {i, j};
			if(grid[i][j] == 'H') hives.push_back({i,j});
		}
	}

	int lo = -1; int hi = N*N/2; //amount of head start to bees

	while(lo < hi){ // in total, O(N^2 log N)
		int mid = lo + (hi - lo + 1) / 2;
		if(works(mid)){
			lo = mid;
		} else {
			hi = mid - 1;
		}
	}

	cout << lo;
}
# Verdict Execution time Memory Grader output
1 Correct 1 ms 852 KB Output is correct
2 Correct 1 ms 852 KB Output is correct
3 Correct 1 ms 852 KB Output is correct
4 Correct 1 ms 852 KB Output is correct
5 Correct 1 ms 852 KB Output is correct
6 Correct 1 ms 852 KB Output is correct
7 Correct 380 ms 2408 KB Output is correct
8 Correct 1 ms 852 KB Output is correct
9 Correct 1 ms 848 KB Output is correct
10 Correct 1 ms 840 KB Output is correct
11 Correct 1 ms 852 KB Output is correct
12 Incorrect 3 ms 980 KB Output isn't correct
13 Incorrect 2 ms 988 KB Output isn't correct
14 Correct 2 ms 964 KB Output is correct
15 Correct 1 ms 852 KB Output is correct
16 Correct 1 ms 852 KB Output is correct
17 Correct 1 ms 852 KB Output is correct
18 Correct 1 ms 852 KB Output is correct
19 Correct 2 ms 968 KB Output is correct
20 Correct 1 ms 852 KB Output is correct
21 Correct 2 ms 972 KB Output is correct
22 Correct 2 ms 980 KB Output is correct
23 Correct 2 ms 980 KB Output is correct
24 Correct 3 ms 980 KB Output is correct
25 Correct 3 ms 980 KB Output is correct
26 Correct 2 ms 980 KB Output is correct
27 Correct 3 ms 980 KB Output is correct
28 Correct 2 ms 980 KB Output is correct
29 Correct 3 ms 980 KB Output is correct
30 Correct 3 ms 992 KB Output is correct
31 Correct 3 ms 968 KB Output is correct
32 Correct 3 ms 980 KB Output is correct
33 Correct 94 ms 1328 KB Output is correct
34 Correct 60 ms 1324 KB Output is correct
35 Correct 43 ms 1236 KB Output is correct
36 Correct 134 ms 1368 KB Output is correct
37 Correct 83 ms 1412 KB Output is correct
38 Correct 48 ms 1408 KB Output is correct
39 Correct 154 ms 1500 KB Output is correct
40 Correct 103 ms 1492 KB Output is correct
41 Correct 74 ms 1492 KB Output is correct
42 Correct 178 ms 1568 KB Output is correct
43 Correct 120 ms 1568 KB Output is correct
44 Correct 84 ms 1584 KB Output is correct
45 Correct 209 ms 1660 KB Output is correct
46 Correct 156 ms 1672 KB Output is correct
47 Correct 102 ms 1676 KB Output is correct
48 Correct 326 ms 1780 KB Output is correct
49 Correct 178 ms 1764 KB Output is correct
50 Correct 142 ms 1748 KB Output is correct
51 Correct 341 ms 1852 KB Output is correct
52 Correct 206 ms 1876 KB Output is correct
53 Correct 159 ms 1884 KB Output is correct
54 Correct 358 ms 1968 KB Output is correct
55 Correct 231 ms 1956 KB Output is correct
56 Correct 152 ms 1976 KB Output is correct
57 Correct 411 ms 2068 KB Output is correct
58 Correct 257 ms 2124 KB Output is correct
59 Correct 173 ms 2088 KB Output is correct
60 Correct 457 ms 2180 KB Output is correct
61 Correct 388 ms 2184 KB Output is correct
62 Correct 227 ms 2204 KB Output is correct
63 Correct 305 ms 2320 KB Output is correct
64 Correct 310 ms 2188 KB Output is correct
65 Correct 272 ms 2196 KB Output is correct
66 Correct 296 ms 2196 KB Output is correct
67 Correct 326 ms 2192 KB Output is correct
68 Correct 339 ms 2240 KB Output is correct
69 Correct 337 ms 2260 KB Output is correct
70 Correct 334 ms 2260 KB Output is correct
71 Correct 303 ms 2260 KB Output is correct
72 Incorrect 801 ms 2260 KB Output isn't correct
73 Incorrect 391 ms 2756 KB Output isn't correct
74 Correct 337 ms 2816 KB Output is correct
75 Correct 334 ms 2840 KB Output is correct
76 Correct 370 ms 2876 KB Output is correct
77 Correct 305 ms 2772 KB Output is correct
78 Correct 359 ms 2748 KB Output is correct
79 Correct 327 ms 2692 KB Output is correct
80 Correct 327 ms 2780 KB Output is correct
81 Correct 329 ms 2696 KB Output is correct
82 Correct 322 ms 2744 KB Output is correct
83 Correct 403 ms 2604 KB Output is correct
84 Correct 343 ms 2752 KB Output is correct
85 Correct 361 ms 2608 KB Output is correct
86 Correct 337 ms 2612 KB Output is correct
87 Correct 363 ms 2600 KB Output is correct
88 Correct 317 ms 2516 KB Output is correct
89 Correct 318 ms 2520 KB Output is correct
90 Correct 407 ms 2524 KB Output is correct
91 Correct 400 ms 2520 KB Output is correct
92 Correct 353 ms 2520 KB Output is correct