Linked List + Check Palindrome

PHOTO EMBED

Thu Dec 15 2022 10:56:01 GMT+0000 (Coordinated Universal Time)

Saved by @Beluga #java #linkedlist 

import java.util.*;
public class LinkedList {
    public static class Node{
        int data;
        Node next;
        public Node (int data) {
            this.data = data;
            this.next = null;
        }
    }
    public static Node head;
    public static Node tail;
    public static int size;

    public void addFirst(int data){
        Node newNode=new Node(data);
        size++;
        if(head==null){
            head=tail=newNode;
            return;
        }
        newNode.next=head;
        head=newNode;
    }

    public void addLast(int data){
        Node newNode= new Node(data);
        tail.next=newNode;
        newNode.next=null;
        tail=newNode;
    }

    public void add(int idx, int data){
        if(idx==0){
            addFirst(data);
        }
        else{
            Node newNode=new Node(data);
            size++;
            Node temp=head;
            int i=0;
            while(i<idx-1){
                temp=temp.next;
                i++;
            }
            newNode.next=temp.next;
            temp.next=newNode;
        }
    }

    public void printLL(LinkedList ll){
        Node temp=ll.head;
        while(temp!=null){
            System.out.print(temp.data + "->");
            temp=temp.next;
        }
        System.out.println("null");
    }

    public Node findMid(Node head){
        Node slow=head;
        Node fast=head;
        while(fast!=null &&  fast.next!=null){
            slow=slow.next;
            fast=fast.next.next;
        }
        return slow;
    }

    public boolean checkPalindrome(){
        if(head==null || head.next==null) return true;
        Node midNode=findMid(head);
        Node prev=null;
        Node curr=midNode;
        Node next;
        while(curr!=null){
            next=curr.next;
            curr.next=prev;
            prev=curr;
            curr=next;
        }
        Node right=prev;
        Node left=head;
        while(right!=null){
            if(left.data!=right.data) return false;
            left = left.next;
            right=right.next;
        }
        return true;

    }

    public static void main(String[] args){
        LinkedList ll = new LinkedList();
        ll.addFirst(1);
        ll.addLast(2);
        ll.addLast(3);
        ll.addLast(1);
        ll.add(3,2);
        //ll.printLL(ll);
        System.out.println(ll.checkPalindrome());

    }
}
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