Java Program to determine whether a singly linked list is the palindrome

Java Program to determine whether a singly linked list is the palindrome

In this example, we will create a java program to check whether given singly linked list is a palindrome or not. A palindromic list is the one that is equivalent to the reverse of itself.

Program:

public class Main {  

class Node{  
int data;  
Node next;  

public Node(int data) {  
this.data = data;  
this.next = null;  
}  
}  

public int size;  
public Node head = null;  
public Node tail = null;  

public void addNode(int data) {  
Node newNode = new Node(data);  

if(head == null) {  
head = newNode;  
tail = newNode;  
}  
else {  
tail.next = newNode;  
tail = newNode;  
}  
size++;  
}  

public Node reverseList(Node temp){  
Node current = temp;  
Node prevNode = null, nextNode = null;  

while(current != null){  
nextNode = current.next;  
current.next = prevNode;  
prevNode = current;  
current = nextNode;  
}  
return prevNode;  
}  

public void isPalindromeLL(){  
Node current = head;  
boolean flag = true;  

int mid = (size%2 == 0)? (size/2) : ((size+1)/2);  

for(int i=1; i<mid; i++){  
current = current.next;  
}  

Node revHead = reverseList(current.next);  

while(head != null && revHead != null){  
if(head.data != revHead.data){  
flag = false;  
break;  
}  
head = head.next;  
revHead = revHead.next;  
}  

if(flag)  
System.out.println("Given singly linked list is a palindrome");  
else  
System.out.println("Given singly linked list is not a palindrome");  
}  

public void display() {  
Node current = head;  

if(head == null) {  
System.out.println("List is empty");  
return;  
}  
System.out.println("Nodes of singly linked list: ");  
while(current != null) {  
System.out.print(current.data + " ");  
current = current.next;  
}  
System.out.println();  
}  

public static void main(String[] args) {  

Main sList = new Main();  

sList.addNode(1);  
sList.addNode(2);  
sList.addNode(3);  
sList.addNode(2);  
sList.addNode(1);  

sList.display();  

sList.isPalindromeLL();  
}  
}