反转双向链表

问题

给你一条双向链表。请使用一趟扫描完成反转。

代码

    
    public static class DoubleNode {
        int value;
        DoubleNode last;
        DoubleNode next;

        public DoubleNode(int value) {
            this.value = value;
        }
    }
    // 反转双向链表
    public static DoubleNode reverseList(DoubleNode head) {
        DoubleNode pre = null;
        DoubleNode next = null;
        while (head != null) {
            next = head.next;
            head.next = pre;
            head.last = next;
            pre = head;
            head = next;
        }
        return pre;
    }