Question

Java program to implement circular linked list.

public class CircularLinkedList  {

    
    private Node tail;
    private int size;
    
    public CircularLinkedList() {
        tail= null;
        size = 0;

    }



     public int size(){
        return size;
    }

 
    public boolean isEmpty()
    {
        return size==0;
    }
    
        
        //if list is not empty return the first element
     
    public E first() {
        if (isEmpty()) return null;
        //code here
        return 0;
    }
  

    
        
        //if list not empty return last element
     
    public E last() {
        if (isEmpty()) return null;
        return tail.getElement();
    }

    /*
        move tail to the next node
     */
    public void rotate()
    {
    }

    /*
        add element to the first of the linked list
        increase the size
     */
    public void addFirst(E e)
    {
        
    }

    /*
        add element to the end of the linked list
        increase size
     */
    public void addLast(E e)
    {
    }

    /*
        take out the first element
        decrease the size
        return first element or null


     */
    public E removeFirst()
    {
        return null;
    }

------------------------------------------------------------------------------------------------------

implements

public class Node {
    // Instance variables:
    //element = data
    private E element;
    private Node next;
    /** Creates a node with null references to its element and next node. */
    public Node() {
        this(null, null);
    }
    /** Creates a node with the given element and next node. */
    public Node(E e, Node n) {
        element = e;
        next = n;
    }
    // Accessor methods:
    public E getElement() {
        return element;
    }
    public Node getNext() {
        return next;
    }
    // Modifier methods:
    public void setElement(E newElem) {
        element = newElem;
    }
    public void setNext(Node newNext) {
        next = newNext;
    }
}

Answer 1

public class CircularLinkedList {

public int size =0;
public Node head=null;
public Node tail=null;

//add a new node at the start of the linked list
public void addNodeAtStart(int data){
System.out.println("Adding node " + data + " at start");
Node n = new Node(data);
if(size==0){
head = n;
tail = n;
n.next = head;
}else{
Node temp = head;
n.next = temp;
head = n;
tail.next = head;
}
size++;
}

public void addNodeAtEnd(int data){
if(size==0){
addNodeAtStart(data);
}else{
Node n = new Node(data);
tail.next =n;
tail=n;
tail.next = head;
size++;
}
System.out.println("\nNode " + data + " is added at the end of the list");
}

public void deleteNodeFromStart(){
if(size==0){
System.out.println("\nList is Empty");
}else{
System.out.println("\ndeleting node " + head.data + " from start");
head = head.next;
tail.next=head;
size--;
}
}

public int elementAt(int index){
if(index>size){
return -1;
}
Node n = head;
while(index-1!=0){
n=n.next;
index--;
}
return n.data;
}

//print the linked list
public void print(){
System.out.print("Circular Linked List:");
Node temp = head;
if(size<=0){
System.out.print("List is empty");
}else{
do {
System.out.print(" " + temp.data);
temp = temp.next;
}
while(temp!=head);
}
System.out.println();
}

//get Size
public int getSize(){
return size;
}

public static void main(String[] args) {
CircularLinkedList c = new CircularLinkedList();
c.addNodeAtStart(3);
c.addNodeAtStart(2);
c.addNodeAtStart(1);
c.print();
c.deleteNodeFromStart();
c.print();
c.addNodeAtEnd(4);
c.print();
System.out.println("Size of linked list: "+ c.getSize());
System.out.println("Element at 2nd position: "+ c.elementAt(2));
}

}

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