单链表反转的2种方法

Posted 2020-06-13

 1 public class ReverseDemo {
 2 
 3     /**
 4      *  单链表反转的两种方法
 5      */
 6     public static void main(String[] args) {
 7         Node head =new Node("a");
 8         Node node2=new Node("b");
 9         Node node3=new Node("c");
10         head.setNext(node2);
11         node2.setNext(node3);
12         Node p=head;
13         System.out.print("链表反转前");
14         while(p!=null){
15             System.out.print(p.getData());
16             p=p.getNext();
17         }
18          Node q=reverse2(head);
19         System.out.print("链表反转后");
20         while(q!=null){
21             System.out.print(q.getData());
22             q=q.getNext();
23         }
24 
25     }
26     public static Node reverse1(Node head){
27         if(head ==null||head.getNext()==null)        //递归，找到尾节点，
28             return head;
29         Node reversehead=reverse1(head.getNext());    //将尾节点设置成新头结点
30         head.getNext().setNext(head);              //改变指向
31         head.setNext(null);
32         return reversehead;
33         
34     }
35     public static Node reverse2(Node head){    //遍历
36         if(head==null)
37             return head;
38         
39         Node pre=head;
40         Node cur=head.getNext();
41         Node tmp;                           
42         while(cur!=null){
43             tmp=cur.getNext();              //遍历结点，让该结点的后驱结点指向该结点
44             cur.setNext(pre);
45             pre=cur;
46             cur=tmp;
47             
48         }
49         head.setNext(null);              //最早的头结点设置指向null成为尾节点
50         return pre;                     //pre为新的头结点
51         
52         
53     }
54     
55 
56 }

链表反转前abc链表反转后cba