UVa 572 Oil Deposits

UVa 572 Oil Deposits

图的连通性问题，我用的是dfs，如果bfs的话需要建队列，比较麻烦，也没有必要。
以下是我的代码：

#include < stdio.h >
#include < string .h >
const   long  maxn = 108 ;
long  m,n,ans,xd[] = { - 1 , - 1 , 0 , 1 , 1 , 1 , 0 , - 1 },yd[] = { 0 , 1 , 1 , 1 , 0 , - 1 , - 1 , - 1 };
char  a[maxn][maxn];
bool  used[maxn][maxn];
void  dfs( long  x, long  y)
{
    used[x][y] = true ;
     for ( long  k = 0 ;k < 8 ;k ++ )
    {
        long  xx = x + xd[k],yy = y + yd[k];
        if (xx >= 1 && xx <= m && yy >= 1 && yy <= n &&! used[xx][yy] && a[xx][yy] == ' @ ' )
         dfs(xx,yy);
    }
}
int  main()
{
     /*
    freopen("program.in","r",stdin);
    freopen("program.out","w",stdout);
    // */
     while (scanf( " %ld%ld " , & m, & n) == 2 )
    {
        if (m == 0 || n == 0 )  return   0 ;
       getchar();
       memset(a, 0 , sizeof (a));
       memset(used, false , sizeof (used));
        //   Clear
        for ( long  i = 1 ;i <= m;i ++ )
       {
           for ( long  j = 1 ;j <= n;j ++ )
            scanf( " %c " , & a[i][j]);
          getchar();
       }
        //   Read In
       ans = 0 ;
        for ( long  i = 1 ;i <= m;i ++ )
          for ( long  j = 1 ;j <= n;j ++ )
            if ( ! used[i][j] && a[i][j] == ' @ ' )
           {
              dfs(i,j);
              ans ++ ;
           }
       printf( " %ld\n " ,ans);
    }
return   0 ;
}