棋盘算法实现，不同形状的L型骨牌覆盖给定棋盘上除特殊方格以外的所有方格，且任何2个L型骨牌不得重叠覆盖。-Checkerboard algorithm, different shapes of the L-type domino coverage given on the board in addition to the special box outside the box, and any two L-shaped domino shall not be overlapped.