1 #include<stdio.h> 2 #include<string.h> 3 const int maxn=1000,maxm=25; 4 int vis[maxm][maxm],mat[maxm][maxm],dir[5][3]={{1,0},{0,-1},{-1,0},{0,1}}; 5 int w,h; 6 char s[maxm][maxm]; 7 struct node{ 8     int xpos; 9     int ypos;10     int step;11     void init(int x,int y,int z)12     {13         xpos=x;14         ypos=y;15         step=z;16     }17 }que[maxn];18 int bfs(node sour);19 int main()20 {21     while(scanf("%d%d",&w,&h)==2 && w && h){22         node source;23         for(int i=0;i<h;i++)24             scanf("%s",s[i]);25         memset(mat,0,sizeof(mat));26         for(int i=0;i<h;i++)27         for(int j=0;j<w;j++){28             if(s[i][j]==‘#‘)29                 mat[i][j]=1;30             else if(s[i][j]==‘@‘){31                 mat[i][j]=0;32                 source.xpos=i;33                 source.ypos=j;34             }35             else36                 continue;37         }38       int maxsteps=bfs(source);39       printf("%d\n",maxsteps);40     }41     return 0;42 }43 int bfs(node sour)44 {45     int maxsteps=1;46     sour.step=1;47     int head,tail;48     que[head=tail=0]=sour;49     tail++;50     memset(vis,0,sizeof(vis));51     vis[sour.xpos][sour.ypos]=1;52     while(head!=tail){53         node a=que[head];54         for(int i=0;i<4;i++){55             int nx=a.xpos+dir[i][0];56             int ny=a.ypos+dir[i][1];57             if(nx>=h || ny>=w || nx<0 || ny<0)58                 continue;59             if(vis[nx][ny])60                 continue;61             if(mat[nx][ny])62                 continue;63             node c;64             c.init(nx,ny,a.step+1);65             que[tail]=c;66             vis[nx][ny]=1;67             maxsteps++;68             tail=(tail+1)%maxn;69         }70         head=(head+1)%maxn;71     }72     return maxsteps;73 }