• 经典错误 1：
• 结果：TLE + MLE

#include<bits/stdc++.h>
using namespace std;


int main()
{ 	
	int n,m,x,y,x1,y1;
	int sxy[105][105],sx[4]={-1,1,0,0},sy[4]={0,0,-1,1},cs=0;
	char a[105][105];
	string s;
	queue<pair<int,int>> q; 
	
	cin>>n>>m;
	memset(sxy,-1,sizeof(sxy));
	cs=0;
	for(int i=0;i<n;i++){
		cin>>s;
		for(int j=0;j<m;j++) a[i][j]=s[j];
	}
	if(a[0][0]=='.') q.push(make_pair(0,0));
	while(!q.empty())
	{
		x=q.front().first,y=q.front().second;
		q.pop();
		if(x==n-1 && y==m-1)
		{
			cout<<"Yes"<<endl;
			cs=1;
			break;
		}
		sxy[x][y]=1;
		for(int t=0;t<4;t++)
		{
			x1=x+sx[t];
			y1=y+sy[t];
			if(x1<0 || x1>=n || y1<0 || y1>=m) continue;
			if(sxy[x1][y1]==1) continue;
			if(a[x1][y1]=='.') q.push(make_pair(x1,y1));
		}
	}
	if(cs==0) cout<<"No"<<endl;
	return 0;
}