题目大意：

给出矩阵，从@出发，只能走.，问最多能走几步

解题思路:

bfs

代码:

#include
     
      #include
      
       #include
       
        #include
        
         using namespace std;char mapp[205][205];int vis[205][205];int n,sx,sy,m;int dirx[5]={
   0,0,1,-1};int diry[5]={
   1,-1,0,0};struct point{    int x;    int y;};int isend(int x,int y){    if(x<0||y<0||x>=n||y>=m||vis[x][y]||mapp[x][y]=='#')        return 1;    return 0;}int bfs(){    queue
         
          que;    point now,next;    now.x=sx;    now.y=sy;    que.push(now);    int i;    while(!que.empty())    {        now=que.front();        que.pop();        vis[now.x][now.y]=1;        for(i=0;i<4;i++)        {            next.x=now.x+dirx[i];            next.y=now.y+diry[i];            if(isend(next.x,next.y))                continue;            else            {                que.push(next);            }        }    }    return 0;}int main(){    int i,j;    while(~scanf("%d%d",&m,&n))    {        if(n==0&&m==0) break;        for(i=0;i