编程实现二叉树结构及其相关功能，以存储用户信息，不使用标准模板类的二叉树结构和函数。同时根据二叉树的变化情况，进行相应的平衡操作，即AVL平衡树操作，四种平衡操作都考虑。采用相应的数据结构模拟用户登录系统，其功能包括用户登录、用户密码更新、用户添加和用户删除等。(The programming implements the two fork tree structure and its related functions to store user information and do not use the two forked tree structure and function of the standard template class. At the same time, according to the change of two forked trees, the corresponding balance operation is carried out, that is, the AVL balance tree operation, and the four kinds of balance operation are considered. The user login system is simulated with the corresponding data structure. Its functions include user login, user password update, user addition and user deletion.)