说明：  QC-LDPC码生成矩阵编程，围长为12，无4环
(The program searches for a girth 12 QC-LDPC code given size of sub-matrix, row and column weights. The configuration of sub-matrices could also be changed. The program offers flexibility in constructing girth-12 QC-LDPC codes compared to other algorithms. The program builds a Tanner graph by connecting groups of rows and columns. A connection is made if it does not form less than twelve-cycles. The program may fail to find a code given particular parameters. It also does not find the smallest codes compared to other algorithms. )