在数据加密和数据压缩中常需要对特殊的字符串进行编码。给定的字母表A 由26 个小写英文字母组成A={a,b,…,z}。-In data encryption and data compression is often the need for special encoded string. Given the alphabet A by the 26 lowercase letters of the alphabet composed of A = (a, b, ..., z).