TLE求条

#include<bits/stdc++.h>
using namespace std;
bool  b[105][105];
bool end12=0;
int n,m;
void dfs(int x,int y)
{
    if(x>0&&x<=n&&y<=m&&y>0&&end12==0&&b[x][y]==1)
    {
        if(x==n&&m==y)
        {
            end12=1;
            cout<<"Yes";
            return;
        }
        b[x][y]=0;
        dfs(x,y+1);
        dfs(x,y-1);
        dfs(x-1,y);
        dfs(x+1,y);
        b[x][y]=1;
    }
    return;
}
int main()
{
    cin>>n>>m;
    getchar();
    for(int z=1;z<=n;z++)
    {
        for(int y=1;y<=m;y++)
        {
            if(getchar()=='#')
            {
                b[z][y]=0;
            }
            else
            {
                b[z][y]=1;
            }
        }
        getchar();
    }
    dfs(1,1);
    if(end12==0)
    {
        cout<<"No";
    }
    return 0;
}