牛客-剑指offer-单链表的反转

来源：互联网发布：阿里云测试招聘编辑：程序博客网时间：2024/06/04 19:33

题目：
将一个链表进行反转.

ListNode.java

public class ListNode {    int val;    ListNode next = null;    ListNode(int val) {        this.val = val;        this.next=null;    } }

Solution.java

/** * Created by xizwu on 2017/2/16. */public class Solution {    public ListNode ReverseList(ListNode head) {            if(head==null)                return null;            ListNode pre=null;            ListNode next=null;            while(head !=null){                next=head.next;                head.next=pre;                pre=head;                head=next;            }            return pre;    }     public ListNode insert(ListNode head,int val){        //1. 指向 链表的末尾         ListNode before=head;         if(head==null){             before=new ListNode(val);             return before;         }         while(head.next !=null){             head=head.next;         }         ListNode myNode=new ListNode(val);         head.next=myNode;         //2. 添加一个node         return before;     }     public   void   myprint(ListNode  head){            if(head==null){                System.out.println(" The list is empty");                return;            }            while(head!=null){                System.out.print(head.val+"  ");                head=head.next;           }     }}

maintest.java

/** * Created by xizwu on 2017/2/16. */public class maintest {        public static void main(String[]  args) {            Solution myso = new Solution();            ListNode myhead = null;            ListNode afterResverHead=null;            myhead=myso.insert(myhead, 1);            myhead=myso.insert(myhead, 2);            myhead=myso.insert(myhead, 3);            myso.myprint(myhead);            afterResverHead=myso.ReverseList(myhead);            System.out.println("#################");            myso.myprint(afterResverHead);        }}

最后的结果：

1 2 3 #################
3 2 1

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