用户登录系统模拟

【问题描述】

在登录服务器系统时，都需要验证用户名和密码，如telnet远程登录服务器。用户输入用户名和密码后，服务器程序会首先验证用户信息的合法性。由于用户信息的验证频率很高，系统有必要有效地组织这些用户信息，从而快速查找和验证用户。另外，系统也会经常会添加新用户、删除老用户和更新用户密码等操作，因此，系统必须采用动态结构，在添加、删除或更新后，依然能保证验证过程的快速。请采用相应的数据结构模拟用户登录系统，其功能要求包括用户登录、用户密码更新、用户添加和用户删除等。-User login system simulation

[Problem Descr iption]

When the login server system, you need to verify the user name and password, such as telnet remote login server. After the user enters a user name and password, the server program will first verify the legitimacy of user information. Due to the high frequency of user verification information systems necessary to effectively organize information these users to quickly find and authenticate users. In addition, the system will often add new users, delete the old users and update user passwords and other operations, so the system must be dynamic structure, add, delete, or update, still able to ensure rapid verification process. Please use the appropriate data structure simulated user login system, its functional requirements, including user login, user password update, users add and delete users.