实现二叉检索树的所有操作，包括插入、删除、查找、前驱、后继、最小值、最大值，最重要的是能以树的形式打印(在控制台下)二叉检索树-All binary search tree operations, including insert, delete, search, precursor and successor, minimum, maximum, and most important print in the form of a tree (the console) binary search