#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;
vector<vector<bool>> bees_visited(n, vector<bool>(n));
vector<vector<int>> bees_time(n, vector<int>(n));
queue<pair<int, int>> q;
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;
}
}
}
while (l <= r) {
vector<vector<bool>> mecho_visited(n, vector<bool>(n));
vector<vector<int>> mecho_time(n, vector<int>(n));
queue<pair<int, int>> q;
int eating_time = (l + r) / 2;
// 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';
}#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;
vector<vector<bool>> bees_visited(n, vector<bool>(n));
vector<vector<int>> bees_time(n, vector<int>(n));
queue<pair<int, int>> q;
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;
}
}
}
while (l <= r) {
vector<vector<bool>> mecho_visited(n, vector<bool>(n));
vector<vector<int>> mecho_time(n, vector<int>(n));
queue<pair<int, int>> q;
int eating_time = (l + r) / 2;
// 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:117:2: error: stray '#' in program
117 | }#include <bits/stdc++.h>
| ^
mecho.cpp:117:3: error: 'include' does not name a type
117 | }#include <bits/stdc++.h>
| ^~~~~~~
mecho.cpp:120:11: error: redefinition of 'const int MAX_N'
120 | const int MAX_N = 800;
| ^~~~~
mecho.cpp:4:11: note: 'const int MAX_N' previously defined here
4 | const int MAX_N = 800;
| ^~~~~
mecho.cpp:121:16: error: redefinition of 'std::vector<std::__cxx11::basic_string<char> > field'
121 | vector<string> field(MAX_N);
| ^~~~~
mecho.cpp:5:16: note: 'std::vector<std::__cxx11::basic_string<char> > field' previously declared here
5 | vector<string> field(MAX_N);
| ^~~~~
mecho.cpp:122:5: error: redefinition of 'int n'
122 | int n, s;
| ^
mecho.cpp:6:5: note: 'int n' previously declared here
6 | int n, s;
| ^
mecho.cpp:122:8: error: redefinition of 'int s'
122 | int n, s;
| ^
mecho.cpp:6:8: note: 'int s' previously declared here
6 | int n, s;
| ^
mecho.cpp:124:6: error: redefinition of 'bool valid_sq(int, int)'
124 | bool valid_sq(int x, int y) {
| ^~~~~~~~
mecho.cpp:8:6: note: 'bool valid_sq(int, int)' previously defined here
8 | bool valid_sq(int x, int y) {
| ^~~~~~~~
mecho.cpp:129:6: error: redefinition of 'bool mecho_reached(int, int)'
129 | bool mecho_reached(int mecho_dis, int bees_dis) { return mecho_dis / s < bees_dis; }
| ^~~~~~~~~~~~~
mecho.cpp:13:6: note: 'bool mecho_reached(int, int)' previously defined here
13 | bool mecho_reached(int mecho_dis, int bees_dis) { return mecho_dis / s < bees_dis; }
| ^~~~~~~~~~~~~
mecho.cpp:131:5: error: redefinition of 'int main()'
131 | int main() {
| ^~~~
mecho.cpp:15:5: note: 'int main()' previously defined here
15 | int main() {
| ^~~~
