0分

#include <bits/stdc++.h> 
using namespace std;
char a[101][101];
int n,m,x1,x2,y,y2;
void dfs(int x,int y)
{
    a[x][y]='#';
    if(x-1>=0&&a[x-1][y]=='.') dfs(x-1,y);
    if(x+1<n&&a[x+1][y]=='.') dfs(x+1,y);
    if(y-1>=0&&a[x][y-1]=='.') dfs(x,y-1);
    if(y+1<n&&a[x][y+1]=='.') dfs(x,y+1);
}
int main()
{
    cin>>n>>m;
        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=m;j++)
            {
                cin>>a[i][j];
            }
        }
        x1=1;y=1;x2=n;y2=m; 
        if(a[x2][y2]=='#') cout<<"NO"<<endl;
        else 
        {
            dfs(x1,y);
            if(a[x2][y2]=='.')
            {
                cout<<"YES"<<endl;
            }
            else 
            {
                cout<<"NO"<<endl;   
            }
        }   
    return 0;
}