简单搜索题：

#include
     
       #include
      
        #include
       
         using namespace std; class Node {
   public: int x,y; }; Node queue[424]; int d[4][2]={
   0,-1,1,0,0,1,-1,0}; char map[24][24]; int BFS( int x, int y ) {
   int end =0 ,first = 0;    Node  t;    t.x = x;    t.y = y;    queue[end]=t;    end++; while( first < end )    {
   for( int i=0; i<4 ; i++ )       {
   int dx = queue[first].x + d[i][0]; int dy = queue[first].y + d[i][1]; if( map[dx][dy] == '.' )         {
              t.x = dx;            t.y = dy;            map[dx][dy]='#';            queue[end] =  t;            end++;            }       }       first++;    }    return end; } int main( ) {
   int n,m; while( scanf( "%d%d",&n,&m ),n )    {
         memset( map , 0, sizeof( map ) ); int x,y; for( int i = 1 ; i<= m ;i++ )       {
             scanf( "%s",map[i]+1 ); for( int j = 1; j<= n  ;j++ )           {
   if( map[i][j]=='@' )               {
                     x = i ;                   y = j; break;                      }                  }              }          map[x][y] = '#';       printf( "%d\n",BFS( x , y ) );    } return 0; }