Getting wrong answer for some test cases

#1

/**

  • 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 ListNode reverseList(ListNode head) {
if(head==null || head.next==null)
return head;

    ListNode prev=head;
    ListNode cur=prev.next;
    ListNode n= cur.next;
    
    while(cur.next!=null)
    {
        cur.next=prev;
        prev=cur;
        cur=n;
        n=n.next;
    }
    cur.next=prev;
    head.next=null;
    head=cur;
    return head;
}

public boolean isPalindrome(ListNode head) {
    
    if(head==null || head.next==null)
        return true;
    ListNode head1=head;
    ListNode rev=reverseList(head);
    
    while(head1!=null)
    {
        if(head1.val==rev.val)
        {
            head1=head1.next;
            rev=rev.next;
        }
        else
            return false;
    }
    return true;
    
}

}

this is the code and I’m getting wrong answer for list [1,1,2,1] but reverse function gives right answer for that list. what is wrong?

#2

@Kapsime_S,

For reverse do:

    private ListNode reverseList(ListNode head) {
        ListNode curr = head;
        ListNode prev = null;
        ListNode next = null;
        
        while(curr != null) {
            next = curr.next;
            curr.next = prev;
            prev = curr;
            curr = next;
        }
        
        return prev;
    }
#3

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