鏈表問題——反轉單向鏈表和雙向鏈表

import java.util.*;
//單向鏈表結點
class test{
    public class Node{
        public int value;
        public Node next;
        public Node(int data){
            this.value = data;
        }
    }

    //反轉單向鏈表
    public Node reverseList(Node head){
        Node pre = null;
        Node next = null;
        while(head!=null){
            next = head.next;
            head.next = pre;
            pre = head;
            head = next;
        }
        return head;
    }

    //雙向鏈表結點
    public class DoubleNode{
        public int value;
        public DoubleNode last;
        public DoubleNode next;
        public DoubleNode(int data){
            this.value = data;
        }
    }

    //反轉雙向鏈表
    public 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 head;
    }
}