牛客-剑指offer-单链表的反转

2019-11-08 03:27:31

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来源：转载

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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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