线性表的链表实现：插入、删除、翻转.链表翻转是把数据逆序（变成降序），注意，头结点不动。翻转后要再翻转一次，恢复升序后才能插入新元素，否则会出错。-List realize linear table: insert, delete, flip. List of data inversion is to reverse (into descending), note that the first fixed node. Flip flip again after the first, after