特殊方格必位于4个较小子棋盘之一中,其余3个子棋盘无特殊方格 用分治法解决棋盘覆盖问题算法接单明了。-Special grid must be located in one of the four smaller sub-chessboard, the remaining three sub-chessboard squares divide-and-conquer method to solve the chessboard coverage problem algorithm orders