实现红黑树的所有操作，包括插入、删除、查找、前驱、后继、最大值、最小值，最重要的是能够以树形打印(在控制台下)红黑树-Red-black tree of all operations, including insert, delete, search, precursor and successor, maximum, minimum, and most important to be able to print a tree (red-black tree under the console)