Reverse a linked list.

public class OneLinkNode {
  public int data;
  public OneLinkNode next; public OneLinkNode(int k) {
   data = k;
   next = null;
  } public OneLinkNode() {
   this(0); }
 public static void main(String args[]) {
   int n = 7;
   OneLinkNode head = create(n);
   
   insert(head, 3, 30);  OneLinkNode p = head;
   for (int i = 0; i < n + 1; i++) {
    System.out.print(p.data + " ");
    p = p.next;
   }  System.out.println();
   delete(head, 4);  p = head;
   for (int i = 0; i < n; i++) {
    System.out.print(p.data + " ");
    p = p.next;
   }  
   head=reverse3(head);
   
   
   System.out.println();  p = head;
   for (int i = 0; i < n; i++) {
    System.out.print(p.data + " ");
    p = p.next;
   }
   
   
   System.out.println();
   
   OneLinkNode a = new OneLinkNode();
   a.data=1;
   OneLinkNode b = new OneLinkNode();
   b.data=2;
   revert(a, b);
   System.out.print(a.data+" "+b.data);
   
  } 
  public static OneLinkNode reverse(OneLinkNode head,int n){
   
   OneLinkNode[] p=new OneLinkNode[n];
   p[0]=head;
   for(int i=0;i<n-1;i++)
   {
    p[i+1]=p[i].next;
   }
   
   p[0].next=null;
   for(int i=0;i<n-1;i++)
   {
    p[i+1].next=p[i];
   }
   
   return p[n-1];
   
  }

public static OneLinkNode reverse2(OneLinkNode head,int n){
   
     OneLinkNode p1=head;
     OneLinkNode p2=head.next;
     OneLinkNode p3=head.next;
     OneLinkNode temp;
   p1.next=null;
    for(int i=0;i<n;i++)
    { p2=p3.next;
      p3.next=p1;
      p1=p2;
     //    revert(p1,p3);
      temp=p1;
   p1=p3;
   p3=temp;
      
    }
    p2.next=p1;
    return p2;
  }
  
  
  
  public static OneLinkNode reverse3(OneLinkNode head){
   
      OneLinkNode p1=head;
      OneLinkNode p2=head.next;
      OneLinkNode p3=head.next;
      OneLinkNode temp;
    p1.next=null;
 while(p2.next!=null)
     { p2=p3.next;
       p3.next=p1;
       p1=p2;
      //    revert(p1,p3);
       temp=p1;
    p1=p3;
    p3=temp;
       
     }
     p2.next=p1;
     return p2;
   }

public static void revert(OneLinkNode a,OneLinkNode b){
  OneLinkNode temp;
  temp=a;
  a=b;
  b=temp;
  
 }

 

public static OneLinkNode create(int n) { // 建立单链表
   OneLinkNode rear, q, head = null;
   if (n > 0) {   int k = (int) (Math.random() * 100);
    head = new OneLinkNode(k);
    rear = head;
    for (int i = 0; i < n - 1; i++) {
     k = (int) (Math.random() * 100);
     q = new OneLinkNode(k);
     rear.next = q;
     rear = q;   }
  }
   return head;
  }

public static boolean insert(OneLinkNode head, int n, int data) {// 在第n个后插入data
   if (head == null)
    return false;
   OneLinkNode p = head;
   for (int i = 0; i < n - 1; i++) {
    p = p.next;
   }
   OneLinkNode newNode = new OneLinkNode();
   newNode.data = data;
   newNode.next = p.next;
   p.next = newNode;
   return true;
  } public static boolean delete(OneLinkNode head, int n) {// 把第n个删除
   if (head == null)
    return false;
   OneLinkNode p1 = head;
   for (int i = 0; i < n - 2; i++) {
    p1 = p1.next;
   }
   p1.next = p1.next.next;
   return true;
  }}