题解

#include <bits/stdc++.h>
using namespace std;

const int N = 1005;
int n, m, k,sx,sy,ex,ey;
char a[N][N];
int vis[N][N];
int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};
struct node {
int x, y;
};
queue<node> q;

void bfs(){
memset(vis, -1, sizeof vis);
q.push({sx,sy});
vis[sx][sy] = 0;
while(!q.empty()){
node cur = q.front(); q.pop();
int x = cur.x, y = cur.y;
for (int i = 0; i < 4; i++) {
for(int d=1; d<=k; d++) {
int nx = x + dx[i]*d, ny = y + dy[i]*d;
if(nx < 1 || nx > n || ny < 1 || ny > m || a[nx][ny] == '#' ) break;
if(vis[nx][ny]!=-1){ //已走过
if(vis[nx][ny] <= vis[x][y]) break; //同方向后续不会产生更优解
}else{ //没走过，正常入队
q.push({nx,ny});
vis[nx][ny] = vis[x][y] + 1;
}
}
}
}
}

int main() {
cin >> n >> m >> k;
for (int i =1; i <= n; i++) {
for (int j = 1; j <= m; j++) {
cin >> a[i][j];
}
}
cin >> sx >> sy >> ex >> ey;
bfs();
cout << vis[ex][ey];
return 0;
}