数据结构 严蔚敏老师书中平衡二叉排序树AVL的实现，添加了书中缺少的部分，包括右平衡操作和最难的删除操作。-Yan Wei-min data structure teacher book AVL balanced binary search tree implementation, adding an integral part of the book, including the right balance of the operation and remove the most difficult operations.