题解

#include <bits/stdc++.h>
using namespace std;
const int N = 50;
int dir[4][2] = {0, 1, 1, 0, 0, -1, -1, 0};
struct node{
    int x, y, step;
};
int r, c;
char a[N][N];
bool vis[N][N] = {0};
int bfs(int x, int y){
    vis[x][y] = true;
    queue<node> q;
    q.push({x, y, 1});
    while(q.size()){
        node now = q.front();
        q.pop();
        for(int i = 0; i < 4; i++){
            int nx = now.x + dir[i][0];
            int ny = now.y + dir[i][1];
            int step = now.step + 1;
            if(nx >= 0 && nx < r && ny >= 0 && ny < c && !vis[nx][ny] && a[nx][ny] == '.'){
                vis[nx][ny] = true;
                q.push({nx, ny, step});
            }
            if(nx == r - 1 && ny == c - 1){
                return step;
            }
        }
    }
}
int main(){
    cin >> r >> c;
    for(int i = 0; i < r; i++){
        for(int j = 0; j < c; j++){
            cin >> a[i][j];
        }
    }
    cout << bfs(0, 0);
    return 0;
}