欧几里得算法，很详尽的解释说明，扩展欧几里得算法，求最大公约数-Euclidean algorithm, a very detailed explanation, extended Euclidean algorithm, find the greatest common divisor

C#实现扩展欧几里得算法，加密解密算法中常用。-C# implementation of extended Euclidean algorithm, encryption and decryption algorithms commonly used.