#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
#define ft first
#define se second
#define NAME "A"
#define file freopen(NAME".INP","r",stdin); freopen(NAME".OUT","w",stdout);
#define sdf ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
const int MOD = 1e9 + 7;
const int N = 800 + 5, INF = 1e15;
int dx[4] = {0, 0, -1, 1};
int dy[4] = {-1, 1, 0, 0};
char a[N][N];
int dis[N][N], vis[N][N] = {INF};
bool f = false;
int n, step, homex, homey, mx, my;
bool bfs(int len, int x, int y){
vis[x][y] = len;
queue<tuple<int, int, int>> q;
q.push({x, y, 0});
while(!q.empty()){
const auto [sx, sy, cur] = q.front(); q.pop();
int dist = (cur + 1) / step;
for(int i = 0;i < 4;++i){
int u = sx + dx[i], v = sy + dy[i];
if(u < 1 || v < 1 || v > n || u > n) continue;
if(a[u][v] == 'G' && (cur + 1) < vis[u][v] && dist < dis[u][v] - (len / step)){
vis[u][v] = cur + 1;
q.push({u, v, cur + 1});
}
}
}
for(int i = 0;i < 4;++i){
int u = homex + dx[i], v = homey + dy[i];
if(vis[u][v] != INF && a[u][v] == 'G' || a[u][v] == 'M') && vis[u][v] / step < dis[u][v] - (len / step)){
return true;
}
}
return false;
}
int32_t main(){
sdf
cin >> n >> step;
queue<pair<int, int>> q;
for(int i = 1;i <= n;++i){
for(int j = 1;j <= n;++j){
cin >> a[i][j];
dis[i][j] = INF;
if(a[i][j] == 'H'){
q.push({i, j});
dis[i][j] = 0;
}
else if(a[i][j] == 'D'){
homex = i; homey = j;
}
else if(a[i][j] == 'M'){
mx = i; my = j;
}
}
}
while(!q.empty()){
const auto [x, y] = q.front(); q.pop();
for(int i = 0;i < 4;++i){
int u = x + dx[i];
int v = y + dy[i];
if(u < 1 || v < 1 || u > n || v > n) continue;
if(dis[u][v] == INF && (a[u][v] == 'G' || a[u][v] == 'M')){
dis[u][v] = dis[x][y] + 1;
q.push({u, v});
}
}
}
int l = 1, r = INF;
int ans =0;
while(l <= r){
int mid = (l + r) / 2;
for(int i = 1;i <= n;++i){
for(int j = 1;j <= n;++j){
vis[i][j] = INF;
}
}
if(bfs(mid * step, mx, my)){
l = mid + 1;
ans = mid;
}
else{
r = mid - 1;
}
}
cout << ((ans >= 1) ? ans : -1) ;
return 0;
}
Compilation message
mecho.cpp: In function 'bool bfs(ll, ll, ll)':
mecho.cpp:40:23: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
40 | if(vis[u][v] != INF && a[u][v] == 'G' || a[u][v] == 'M') && vis[u][v] / step < dis[u][v] - (len / step)){
| ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
mecho.cpp:40:66: error: expected ';' before '[' token
40 | if(vis[u][v] != INF && a[u][v] == 'G' || a[u][v] == 'M') && vis[u][v] / step < dis[u][v] - (len / step)){
| ^
| ;
mecho.cpp:40:60: warning: statement has no effect [-Wunused-value]
40 | if(vis[u][v] != INF && a[u][v] == 'G' || a[u][v] == 'M') && vis[u][v] / step < dis[u][v] - (len / step)){
| ^~~~~~
mecho.cpp:40:63: error: label 'vis' used but not defined
40 | if(vis[u][v] != INF && a[u][v] == 'G' || a[u][v] == 'M') && vis[u][v] / step < dis[u][v] - (len / step)){
| ^~~
