#include<bits/stdc++.h>
using namespace std;
int vis[105][105],dx[5]={0,1,0,1},dy[5]={1,0,1,0};
char sht[105][105];
int ans=0;
int n,m;
void init(){
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			if(sht[i][j]=='#')vis[i][j]=1;
		}
	}
}
void dfs(int x,int y){
	if(x==n&&y==m){
		ans++;
		return;
	}else{
		for(int i=0;i<4;i++){
			if(1<=x+dx[i]&&x+dx[i]<=n&&1<=y+dy[i]&&y+dy[i]<=n){
				if(vis[x+dx[i]][y+dy[i]]!=1){
					vis[x+dx[i]][y+dy[i]]=1;
					dfs(x+dx[i],y+dy[i]);
				}
			}
		}
	}	
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			cin>>sht[i][j];
		}
	}
	init();
	dfs(1,1);
	if(ans>=1)cout<<"Yes";
	else cout<<"No";
} 

dalao求助！为何只有70！

我不服！

(但也得服)