234. Palindrome Linked List

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {

    private static ListNode reverse(ListNode head)
    {
        ListNode prev = null;
        ListNode curr = head;
        ListNode after = null;

        while(curr != null)
        {
            after = curr.next ;
            curr.next = prev ;
            prev = curr ;
            curr = after;
        }
        return prev;
    }
    
    
    public boolean isPalindrome(ListNode head) 
    {
        ListNode slow = head ;
        ListNode fast = head ;
        ListNode p1 = head;
        ListNode p2 = head;

        while(fast.next!=null && fast.next.next!=null)
        {
            slow = slow.next;
            fast = fast.next.next;
        }
        ListNode temp = reverse(slow.next);
        slow.next=temp;
        p2=slow.next;

        while(p2!=null)
        {
            while(p1.val != p2.val)
            return false;
            
                p1=p1.next;
                p2=p2.next;
            
        }
        return true;

        
    }
}