poj 1321 棋盘问题

poj 1321 棋盘问题

 
我把所有的棋盘区域记下来，这一只要搜索这些区域即可。

不过这样貌似还没有直接按行搜索快。失败

#include < iostream >
using   namespace  std;
char  map[ 10 ][ 10 ];
int  f[ 10 ][ 10 ],n,k,ans,num_chess;
struct  type
{
        int  x,y;
}chess[ 65 ];
bool  check( int  i,  int  j) // check if it is possible to put it at (i,j)
{
     for ( int  k = 1 ; k <= n; k ++ )  
             if (f[i][k] && k != j) return   false ;
     for ( int  k = 1 ; k <= n; k ++ )
             if (f[k][j] && k != i) return   false ;
     return   true ;
}

void  dfs( int  cnt,  int  numchess )
{ 
      if (cnt == k){ ans ++ ;  return  ; }
      if (numchess > num_chess) return  ;
      int  x = chess[numchess].x,y = chess[numchess].y;
     
      if (check(x,y))
     {
      f[x][y] = 1 ;
      dfs(cnt + 1 ,numchess + 1 );
     } 
     
     f[x][y] = 0 ;
     dfs(cnt, numchess + 1 );
}

int  main()
{
     while (cin >> n >> k)
    {
          if (n ==- 1   &&  k ==- 1 ) break ;
         memset(map, 0 , sizeof  map);
         memset(f, 0 , sizeof  f);
         ans = 0 ;
         num_chess = 0 ;
          for ( int  i = 1 ; i <= n; i ++ )
          for ( int  j = 1 ; j <= n; j ++ )
               {
                         cin >> map[i][j];
                          if (map[i][j] == ' # ' )
                         {
                                           num_chess ++ ;
                                           chess[num_chess].x = i; chess[num_chess].y = j; 
                         }
               }
         dfs( 0 , 1 );
         cout << ans << endl;
    }
    
    system( " pause " );
     return   0 ;
}