判断链表是否为回文结构

对于一个链表，请设计一个时间复杂度为O(n),额外空间复杂度为O(1)的算法，判断其是否为回文结构。

Code

//coding=utf8                                                                                                         /*****************************************************                                                                 @Author: Alex                                                                                                         @Created Time : Tue 03 Sep 2019 07:36:51 AM CST                                                                                                                                                                                             @File Name: palindromeList.java                                                                                       @Blog: https://blog.csdn.net/weixin_43336281                                                                                                                                                                                                ****************************************************/                                                                
public class palindromeList{                                                                                              
	public static class Node{                                                                                                 		
		public int value;                                                                                                     
		public Node next;                                                                                                                                                                                                                           
		public Node(int data){                                                                                                    
		this.value = data;                                                                                                
		}                                                                                                                 
	}                                                                                                                                                                                                                                           

	public static boolean isPalindrome(Node head){                                                                            
		if(head == null || head.next == null)                                                                                     
			return true;                                                                                                      
		
		Node n1 = head;                                                                                                       
		Node n2 = head;                                                                                                                                                                                                                             

		while(n2.next != null && n2.next.next != null){                                                                           
			n1 = n1.next;                                                                                                         
			n2 = n2.next.next;                                                                                                
		}      
        
        n2 = n1.next;                                                                                                         
        n1.next = null;                                                                                                       
        Node n3 = null;                                                                                                                                                                                                                             

		while(n2 != null){                                                                                                        
			n3 = n2.next;                                                                                                         
			n2.next = n1;                                                                                                         
			n1 = n2;                                                                                                              
			n2 = n3;                                                                                                          
		}                                                                                                                                                                                                                                           

		n3 = n1;  //n3 is last node                                                                                           
		n2 = head;                                                                                                            
		boolean res = true;                                                                                                                                                                                                                         

		while(n1 != null && n2 != null){                                                                                          
			if(n1.value != n2.value){                                                                                                 
				res = false;                                                                                                          
				break;                                                                                                            
			}                                                                                                                     
			n1 = n1.next;                                                                                                         
			n2 = n2.next;                                                                                                     
		}                                                                                                                                                                                                                                           

		n1 = n3.next;                                                                                                         
		n3.next = null;                                                                                                                                                                                                                             

		while(n1 != null){    
        	n2 = n1.next;                                                                                                         
        	n1.next = n3;                                                                                                         
        	n3 = n1;                                                                                                              
        	n1 = n2;                                                                                                          
        }                                                                                                                     
        return res;                                                                                                       }                                                                                                                 }