16 反转链表

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描述：
实现代码：
import java.util.ArrayList;import java.util.Arrays;import java.util.Collection;class ListNode {int val;ListNode next = null;ListNode(int val) {this.val = val;}}public class ReverseList {private static ListNode head,tail;   // 链表的 首节点和尾节点public ReverseList() {// TODO Auto-generated constructor stubhead=tail=null;}// 添加一组数据public static void add (Collection<Integer> c){Object[] a = c.toArray();int numNew = a.length;if (numNew == 0)return ;for (Object o : a) {addTail((int) o);}}// 尾插法public static void addTail(int data){ListNode newNode=new ListNode(data);if (tail==null) {head=tail=newNode;}else {tail.next=newNode;tail=newNode;}}// 打印链表private static void display(ListNode head) {// TODO Auto-generated method stubif (head==null) {return;}System.out.println(head.val);display(head.next);}// 非递归方法private static ListNode ReverseList1(ListNode head) {ListNode newNode=null;ListNode cur=head;ListNode pre=null,next=null;while (cur!=null) {next=cur.next;if (next==null) {newNode=cur;}cur.next=pre;pre=cur;cur=next;}return newNode;}// 递归方法public static ListNode ReverseList(ListNode head) {if (head==null) {return null;}ListNode tail=head;while(tail.next!=null) tail=tail.next;recursive(head);head.next=null;return tail;}private static ListNode recursive(ListNode head){ListNode cur=head;if(cur.next!=null){ListNode    nextNode=recursive(cur.next);nextNode.next=cur;}return cur;}public static void main(String[] args) {// TODO Auto-generated method stubArrayList<Integer> arrayList=new ArrayList<Integer>(Arrays.asList(1,2,3,4,5));add(arrayList);//ListNode node=ReverseList(head);   //递归方法ListNode node1=ReverseList1(head);      //非递归方法display(node1);}}
测试结果：
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