扫描指定目录，并找出需要替换的文件，进行替换操作，可根据程序进行相应的扩展，本程序搜索深度设定为4。-Scanning the specified directory, and find out the need to replace files

Substitution ciphers are probably the most common form of cipher. They work by replacing each letter of the plaintext (and sometimes puntuation marks and spaces) with another letter (or possibly even a random symbol). A monoalphabetic substituti