第二个搜索函数为私有成员函数S a v e S e a r c h，由插入和删除操作来调用。S a v e S e a r c h不仅 包含了S e a r c h的功能，而且可把每一级中遇到的最后一个节点存放在数组l a s t之中-second search function to the private members of a function S S e v e r c h a, insert and delete operation to call. A S S e v e r