Insertion in the Beginning of a Circular Linked List in JAVA

February 18, 2023

Longest subsequence between two strings

JAVA Program to Insert a Node in the Beginning of a Circular Linked List

Insertion in any type of a Linked List is just modification of the address stored in the references of the Nodes, Insertion in the Beginning of a Circular Linked List in JAVA is also achieved using similar minor modification. For insertion in the beginning the address stored in the HEAD now points to the new node and the New Node will now point towards the Node where head was earlier pointing to.

Steps to insert a node in the Beginning of a Circular Linked List

While Insertion in the Beginning of a Circular Linked List in JAVA two cases can be considered.

  • The circular linked is empty –
    • To insert an element in an empty circular list is quite easy.
    • Both the head and the tail points to the very first element in a circular linked list.
  • The circular linked list is not empty –
    • In a circular linked list the first element serves the purpose of a head. It stores the information of the next node of the circular linked.
    • To insert an element in the beginning of the linked list. The new node should point towards the previous Head making it the new head of the circular linked list.
    • The tail is the last node that points back to the first note making the linked list circular because the traversal can be done from start till end.
    • To add a node in the beginning means to change the node tail is referring to newly added node. By doing this the new node will be inserted in the beginning of the circular linked list.
Insertion in beginning of Circular Linked List in java 
public void insertBegin(int element){
        Node newEle = new Node(element);
        if(head == null) {
            head = newEle;
            tail = newEle;
            newEle.next = head;
            newEle.prev=head;
        }
        else {
            head.prev = newEle;
            newEle.prev=tail;
            newEle.next = head;
            tail.next = newEle;
            head=newEle;
        }
        size++;
    }
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Insertion at the end

Insertion at nth position

Deletion in Circular Linked List

Deletion from beginning in Circular Linked List

Deletion from nth position in Circular Linked List

Here is the Algorithm to add a Node at the Beginning of a Linked List

  • addFirst(element)
  • IF Head==Null
    • Head -> newNode
    • Tail -> newNode
    • newNode->next = Head
    • EXIT
  • ELSE
    • Node Temp = head 
    • newNode->next = Temp
    • head = newNode
    • tail->next = Head
    • EXIT

Java code for insertion at beginning in a circular Linked List

Run 
import java.lang.*;
public class Main {
    public static void main(String[] args) {
        Main Obj = new Main();
        Obj.insertBegin(11);
        Obj.insertBegin(22);
        Obj.insertBegin(33);
        Obj.insertBegin(44);
        Obj.insertBegin(55);

        Obj.print();
    }
    public class Node{
        int element;
        Node next;
        public Node(int element) {
            this.element = element;
        }
    }

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

    public void insertBegin(int element){
        Node newEle = new Node(element);
        if(head == null) {
            head = newEle;
            tail = newEle;
            newEle.next = head;
        }
        else {
            newEle.next=head;
            head=newEle;
            tail.next = head;
        }
        size++;
    }

    public void print() {  //print function
        Node current = head;
        if(head == null) {
            System.out.println("List is empty");
        }
        else {
            System.out.println("Nodes of the circular linked list: ");
            do{
                System.out.print(" "+ current.element);
                current = current.next;
            }while(current != head);
            System.out.println();
        }
    }
}

Output

Nodes of the circular linked list: 
 55 44 33 22 11
Run 
import java.lang.*;
public class Main {
    public static void main(String[] args) {
        Main Obj = new Main();

        Obj.insertBegin(11);
        Obj.insertBegin(22);
        Obj.insertBegin(33);
        Obj.insertBegin(44);
        Obj.insertBegin(55);

        Obj.print();

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

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

    public void insertBegin(int element){
        Node newEle = new Node(element);
        if(head == null) {
            head = newEle;
            tail = newEle;
            newEle.next = head;
            newEle.prev=head;
        }
        else {
            head.prev = newEle;
            newEle.prev=tail;
            newEle.next = head;
            tail.next = newEle;
            head=newEle;
        }
        size++;
    }

    public void print() {  //print function
        Node current = head;
        if(head == null) {
            System.out.println("List is empty");
        }
        else {
            System.out.println("Nodes of circular Linked List :");
            do{
                System.out.print(" "+ current.element);
                current = current.next;
            }while(current != head);
            System.out.println();
        }
    }
}

Output

Nodes of circular Linked List :
 55 44 33 22 11

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