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Submission #621406

# Submission time Handle Problem Language Result Execution time Memory
621406 2022-08-03T18:35:31 Z abcisosm5 Mecho (IOI09_mecho) C++17
84 / 100
 889 ms 2416 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 + N; 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 + N; //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;
}

Subtask #1
84.0 / 100.0

# 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 350 ms 2040 KB Output is correct
8 Correct 1 ms 964 KB Output is correct
9 Correct 1 ms 852 KB Output is correct
10 Correct 2 ms 980 KB Output is correct
11 Correct 1 ms 844 KB Output is correct
12 Incorrect 3 ms 980 KB Output isn't correct
13 Incorrect 2 ms 980 KB Output isn't correct
14 Correct 3 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 2 ms 852 KB Output is correct
18 Correct 2 ms 852 KB Output is correct
19 Correct 2 ms 980 KB Output is correct
20 Correct 2 ms 852 KB Output is correct
21 Correct 2 ms 964 KB Output is correct
22 Correct 2 ms 980 KB Output is correct
23 Correct 3 ms 964 KB Output is correct
24 Correct 2 ms 980 KB Output is correct
25 Correct 3 ms 980 KB Output is correct
26 Correct 3 ms 980 KB Output is correct
27 Correct 4 ms 980 KB Output is correct
28 Correct 4 ms 980 KB Output is correct
29 Correct 6 ms 980 KB Output is correct
30 Correct 3 ms 980 KB Output is correct
31 Correct 4 ms 980 KB Output is correct
32 Correct 3 ms 980 KB Output is correct
33 Correct 90 ms 1328 KB Output is correct
34 Correct 59 ms 1324 KB Output is correct
35 Correct 47 ms 1236 KB Output is correct
36 Correct 134 ms 1408 KB Output is correct
37 Correct 69 ms 1408 KB Output is correct
38 Correct 47 ms 1364 KB Output is correct
39 Correct 139 ms 1492 KB Output is correct
40 Correct 95 ms 1504 KB Output is correct
41 Correct 64 ms 1500 KB Output is correct
42 Correct 183 ms 1576 KB Output is correct
43 Correct 118 ms 1572 KB Output is correct
44 Correct 80 ms 1580 KB Output is correct
45 Correct 244 ms 1628 KB Output is correct
46 Correct 139 ms 1636 KB Output is correct
47 Correct 93 ms 1636 KB Output is correct
48 Correct 319 ms 1652 KB Output is correct
49 Correct 178 ms 1620 KB Output is correct
50 Correct 124 ms 1664 KB Output is correct
51 Correct 341 ms 1696 KB Output is correct
52 Correct 238 ms 1620 KB Output is correct
53 Correct 152 ms 1712 KB Output is correct
54 Correct 392 ms 1748 KB Output is correct
55 Correct 251 ms 1748 KB Output is correct
56 Correct 170 ms 1744 KB Output is correct
57 Correct 469 ms 1772 KB Output is correct
58 Correct 276 ms 1748 KB Output is correct
59 Correct 178 ms 1788 KB Output is correct
60 Correct 649 ms 1808 KB Output is correct
61 Correct 360 ms 1804 KB Output is correct
62 Correct 220 ms 1828 KB Output is correct
63 Correct 307 ms 1820 KB Output is correct
64 Correct 326 ms 1824 KB Output is correct
65 Correct 316 ms 1812 KB Output is correct
66 Correct 346 ms 1848 KB Output is correct
67 Correct 308 ms 1824 KB Output is correct
68 Correct 383 ms 1876 KB Output is correct
69 Correct 290 ms 1872 KB Output is correct
70 Correct 336 ms 1884 KB Output is correct
71 Correct 350 ms 1880 KB Output is correct
72 Incorrect 889 ms 1884 KB Output isn't correct
73 Incorrect 371 ms 2392 KB Output isn't correct
74 Correct 332 ms 2400 KB Output is correct
75 Correct 394 ms 2384 KB Output is correct
76 Correct 323 ms 2392 KB Output is correct
77 Correct 335 ms 2396 KB Output is correct
78 Correct 340 ms 2396 KB Output is correct
79 Correct 331 ms 2416 KB Output is correct
80 Correct 349 ms 2328 KB Output is correct
81 Correct 316 ms 2312 KB Output is correct
82 Correct 341 ms 2316 KB Output is correct
83 Correct 334 ms 2324 KB Output is correct
84 Correct 356 ms 2260 KB Output is correct
85 Correct 340 ms 2232 KB Output is correct
86 Correct 345 ms 2236 KB Output is correct
87 Correct 317 ms 2232 KB Output is correct
88 Correct 336 ms 2144 KB Output is correct
89 Correct 310 ms 2136 KB Output is correct
90 Correct 295 ms 2148 KB Output is correct
91 Correct 321 ms 2140 KB Output is correct
92 Correct 305 ms 2204 KB Output is correct