题解在此

#include <iostream>
#include <queue>
using namespace std;
int r,c;
char mp[50][50];
bool vis[50][50];
int dx[4]={0,0,-1,1};
int dy[4]={1,-1,0,0};
struct node{
    int x,y,ans;
};
int main(){
    cin>>r>>c;
    for (int i=1;i<=r;i++){
        for (int j=1;j<=c;j++){
            cin>>mp[i][j];
        }
    }
    queue<node>q;
    q.push({1,1,1});
    vis[1][1]=1;
    while (q.size()){
        node k=q.front();
        q.pop();
        if (k.x==r&&k.y==c){
            cout<<k.ans;
            return 0;
        }
        for (int i=0;i<4;i++){
            int nx=k.x+dx[i];
            int ny=k.y+dy[i];
            if (nx>=1&&nx<=r&&ny>=1&&ny<=c&&vis[nx][ny]==0&&mp[nx][ny]=='.'){
                vis[nx][ny]=1;
                q.push({nx,ny,k.ans+1});
            }
        }
    }
    return 0;
}