C-矩阵，除去第一行、第一列、最后一列外都为0.这样一个C-矩阵可以压缩存储为一维数组，先逐行再第一列的顺序。并且支持存储搜索功能。-C-matrix, removing the first row, first column, the last column are zero outside, so a C-matrix can be stored as a compressed one-dimensional array, then the order of the first column