说明：  平衡二叉树实现一个动态查找表,有三种基本功能:查找,插入删除,还有选项功能:合并两棵平衡二叉树,和分裂两棵平衡二叉树.
(balanced binary tree to achieve a dynamic lookup table, there are three basic functions : to find, delete, insert, functional options : merging two balanced binary tree, and split two balanced binary tree.)