该源码是一个问题的解决方法。问题是给你个长为L的串，串中可以出现n种字符，还给出m个子串，求有多少个长为n的只由这些字串组成的串。输入例子：4 5 6 ABB BCA BCD CAB CDD DDA 结果为2.而5 4 5 E D C B A的结果为625-source of the problem is a solution. The problem is that you have the head of the L series, the series can occur n ch