第二章 链表问题（反转双向链表）

【题目】

实现反转双向链表的函数

    DoubleNode<Integer> reverseDoubleNode(DoubleNode<Integer> head) {if (head == null || head.next == null) {return head;}DoubleNode<Integer> next = null;DoubleNode<Integer> rev = null;while (head != null) {next = head.next;head.next = rev;head.last = next;rev = head;head = next;}return rev;}