1.创建一个双向链表，结点内容可以是任意类型的值； 2.删除一个已创建的双向链表； 3.向表尾添加一个结点；-1 Create a doubly linked list, the contents of the node can be any type of value 2. Delete a doubly linked list has been created 3 to add a node to the end of the table