双向链表反转

双向链表类

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

    public DoubleNode(int data){
        value = data;
    }

}

反转方法

public static DoubleNode revertDoubleList(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;
    }

测试方法

 public static void main(String[] args) {
        DoubleNode node = new DoubleNode(1);
        node.next = new DoubleNode(2);
        node.next.next = new DoubleNode(3);
        node.next.next.last = node.next;
        node.next.last = node;
        node = revertDoubleList(node);
        while (node != null){

            System.out.print(node.value +" ");
            if (node.last != null){
                System.out.print("  node.last:"+node.last.value +" ");
            }
            System.out.println();
            node = node.next;

        }

    }

打印结果

3 
2   node.last:3 
1   node.last:2