enum States { used, free };
class Board    //一盤棋8*8
{
 private:
   char board[8][8];
   States Rows[8], DiagsLR[15], DiagsRL[15];
 public:
   Board();
   ~Board(){}
   bool isAttacked(int, int);
   void Print();
   void PlaceQueen(int, int);
   void RemoveQueen(int, int);
};