#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){
if (x >= 0 && x < n && y >= 0 && y < n && (field[x][y] == 'G' || field[x][y] == 'M'))
return true;
return false;
}
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, r = n * n;
queue <pair <int, int>> q;
while (l <= r){
vector <vector <bool>> bees_visited(n, vector<bool>(n, false));
vector <vector <bool>> mecho_visited(n, vector<bool>(n, false));
vector <vector <int>> bees_time(n, vector<int>(n, 0));
vector <vector <int>> mecho_time(n, vector<int>(n, 0));
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_time[x][y] + 1) / s < 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 mecho_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_time[nx][ny] / s) < bees_time[nx][ny] - eating_time
&& mecho_visited[nx][ny])
mecho_reached = true;
}
if (mecho_reached){
l = eating_time + 1;
}
else{
r = eating_time - 1;
}
}
cout << l - 1 << '\n';
}
Compilation message
mecho.cpp: In function 'int main()':
mecho.cpp:107:1: error: expected '}' at end of input
107 | }
| ^
mecho.cpp:12:1: note: to match this '{'
12 | {
| ^
