Program to Insert a New Node at the End of the Circular Linked List

Q. Program to insert a new node at the end of the circular linked list.

Explanation

In this program, we will create a circular linked list and insert every new node at the end of the list. If the list is empty, then head and tail will point to the newly added node. If the list is not empty, the newly added node will become the new tail of the list. The previous tail will point to new node as its next node. Since it is a circular linked list; the new tail will point to head. In other words, the new node will become last node (tail) of the list, and the previous tail will be the second last node.

Program to insert a new node at the end of the circular linked list

After inserting new node to the end of the list

New represents the newly added node. D is the previous tail. When new is added to the end of the list, it will become new tail and D will point to new.

Algorithm

Define a Node class which represents a node in the list. It has two properties data and next which will point to the next node.
Define another class for creating the circular linked list and it has two nodes: head and tail. It has two methods: addAtEnd() and display() .
addAtEnd() will add the node to the end of the list:
1. It first checks whether the head is null (empty list), then it will insert the node as the head.
2. Both head and tail will point to the newly added node.
3. If the list is not empty, then the newly added node will become the new tail, and previous tail will point to new node as its next node. The new tail will point to the head.
display() will show all the nodes present in the list.
1. Define a new node 'current' that will point to the head.
2. Print current.data till current will points to head again.
3. Current will point to the next node in the list in each iteration.

Solution

Python

#Represents the node of list.
class Node:
  def __init__(self,data):
    self.data = data;
    self.next = None;
 
class CreateList:
  #Declaring head and tail pointer as null.
  def __init__(self):
    self.head = Node(None);
    self.tail = Node(None);
    self.head.next = self.tail;
    self.tail.next = self.head;
    
  #This function will add to the end of the list.
  def addAtEnd(self,data):
    newNode = Node(data);
    #Checks if the list is empty.
    if self.head.data is None:
      #If list is empty, both head and tail would point to new node.
      self.head = newNode;
      self.tail = newNode;
      newNode.next = self.head;
    else:
      #tail will point to new node.
      self.tail.next = newNode;
      #New node will become new tail.
      self.tail = newNode;
      #Since, it is circular linked list tail will point to head.
      self.tail.next = self.head;
 
  #Displays all the nodes in the list
  def display(self):
    current = self.head;
    if self.head is None:
      print("List is empty");
      return;
    else:
        print("Adding nodes to the end of the list: ");
        #Prints each node by incrementing pointer.
        print(current.data),
        while(current.next != self.head):
            current = current.next;
            print(current.data),
        print("\n");
 
class CircularLinkedList:
    cl = CreateList();
    #Adding 1 to the list
    cl.addAtEnd(1);
    cl.display();
    #Adding 2 to the list
    cl.addAtEnd(2);
    cl.display();
    #Adding 3 to the list
    cl.addAtEnd(3);
    cl.display();
    #Adding 4 to the list
    cl.addAtEnd(4);
    cl.display();

Output:

Adding nodes to the end of the list: 
1
Adding nodes to the end of the list: 
1 2
Adding nodes to the end of the list: 
1 2 3
Adding nodes to the end of the list: 
1 2 3 4

C

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
 
//Represents the node of list.
struct node{
    int data;
    struct node *next;
};
 
//Declaring head and tail pointer as null.
struct node *head = NULL;
struct node *tail = NULL;
 
//This function will add the new node at the end of the list.
void addAtEnd(int data){
    //Create new node
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    newNode->data = data;
    //Checks if the list is empty.
    if(head == NULL){
        //If list is empty, both head and tail would point to new node.
        head = newNode;
        tail = newNode;
        newNode->next = head;
    }else {
        //tail will point to new node.
        tail->next = newNode;
        //New node will become new tail.
        tail = newNode;
        //Since, it is circular linked list tail will point to head.
        tail->next = head;
    }
}
 
//This function will display the nodes of circular linked list
void display(){
    struct node *current = head;
    if(head == NULL){
        printf("List is empty");
    }
    else{
        printf("Adding nodes to the end of the list: \n");
         do{
             //Prints each node by incrementing pointer.
            printf("%d ", current->data);
            current = current->next;
        }while(current != head);
        printf("\n");
    }
}
    
int main()
{
    //Adding 1 to the list
   addAtEnd(1);
   display();
   //Adding 2 to the list
   addAtEnd(2);
   display();
   //Adding 3 to the list
   addAtEnd(3);
   display();
   //Adding 4 to the list
   addAtEnd(4);
   display();
   
   return 0;
}

Output:

Adding nodes to the end of the list: 
1
Adding nodes to the end of the list: 
1 2
Adding nodes to the end of the list: 
1 2 3
Adding nodes to the end of the list: 
1 2 3 4

JAVA

public class InsertAtEnd {
    //Represents the node of list.
        public class Node{
            int data;
            Node next;
            public Node(int data) {
                this.data = data;
            }
        }
        
        //Declaring head and tail pointer as null.
        public Node head = null;
        public Node tail = null;
        
        //This function will add the new node at the end of the list.
        public void addAtEnd(int data){
            //Create new node
            Node newNode = new Node(data);
            //Checks if the list is empty.
            if(head == null) {
                 //If list is empty, both head and tail would point to new node.
                head = newNode;
                tail = newNode;
                newNode.next = head;
            }
            else {
                //tail will point to new node.
                tail.next = newNode;
                //New node will become new tail.
                tail = newNode;
                //Since, it is circular linked list tail will points to head.
                tail.next = head;
            }
        }
        
        //Displays all the nodes in the list
        public void display() {
            Node current = head;
            if(head == null) {
                System.out.println("List is empty");
            }
            else {
                System.out.println("Adding nodes to the end of the list: ");
                 do{
                    //Prints each node by incrementing pointer.
                    System.out.print(" "+ current.data);
                    current = current.next;
                }while(current != head);
                System.out.println();
            }
        }
        
        public static void main(String[] args) {
            InsertAtEnd cl = new InsertAtEnd();
            
            //Adding 1 to the list
            cl.addAtEnd(1);
            cl.display();
            //Adding 2 to the list
            cl.addAtEnd(2);
            cl.display();
            //Adding 3 to the list
            cl.addAtEnd(3);
            cl.display();
            //Adding 4 to the list
            cl.addAtEnd(4);
            cl.display();
        }
}

Output:

Adding nodes to the end of the list: 
1
Adding nodes to the end of the list: 
1 2
Adding nodes to the end of the list: 
1 2 3
Adding nodes to the end of the list: 
1 2 3 4

C#

using System; 
namespace CircularLinkedList 
{                     
    public class Program
    {
        //Represents the node of list.
        public class Node<T>{
            public T data;
            public Node<T> next;
            public Node(T value) {
                data = value;
                next = null;
            }
        }
        
        public class CreateList<T>{
            protected Node<T> head = null;             
             protected Node<T> tail = null;
            
            //This function will add the new node at the end of the list.
            public void addAtEnd(T data){
                //Create new node
                Node<T> newNode = new Node<T>(data);
                //Checks if the list is empty.
                if(head == null){
                    head = newNode;
                    tail = newNode;
                    newNode.next = head;
                    
                }else{
                    
                    //tail will point to new node.
                    tail.next = newNode;
                    //New node will become new tail.
                    tail = newNode;
                    //Since, it is circular linked list tail will point to head.
                    tail.next = head;
                }
    
            }
            //Displays all the nodes in the list
            public void display(){
                Node<T> current = head;
                if(head == null){
                    Console.WriteLine("List is empty");
                }
                else{
                    Console.WriteLine("Adding nodes to the end of the list: ");
                    do{
                        //Prints each node by incrementing pointer.
                        Console.Write(" "+ current.data);
                        current = current.next;
                    }while(current != head);
                    Console.WriteLine();
                }        
            }
        }
        
        public static void Main()
        {
            
        CreateList<int> cl = new CreateList<int>();
            
        //Adding 1 to the list
        cl.addAtEnd(1);
        cl.display();
        //Adding 2 to the list
        cl.addAtEnd(2);
        cl.display();
        //Adding 3 to the list
        cl.addAtEnd(3);
        cl.display();
        //Adding 4 to the list
        cl.addAtEnd(4);
        cl.display();
        }    
    }
}

Output:

Adding nodes to the end of the list: 
1
Adding nodes to the end of the list: 
1 2
Adding nodes to the end of the list: 
1 2 3
Adding nodes to the end of the list: 
1 2 3 4

PHP

<!DOCTYPE html>
<html>
<body>
<?php
//Represents the node of list.
class Node{
    public $data;
    public $next;
    function __construct($data){
        $this->data = $data;
        $this->next = NULL;
    }
}
class CreateList{
    //Declaring head and tail pointer as null.
    private $head;
    private $tail;
    function __construct(){
        $this->head = NULL;
        $this->tail = NULL;
    }
    //This function will add the new node at the end of the list.
    function addAtEnd($data){
        //Create new node
        $newNode = new Node($data);
        //Checks if the list is empty.
        if($this->head == NULL){
            //If list is empty, both head and tail would point to new node.
            $this->head = $newNode;
            $this->tail = $newNode;
            $newNode->next = $this->head;
        }
        else{
            //tail will point to new node.
            $this->tail->next = $newNode;
            //New node will become new tail.
            $this->tail = $newNode;
            //Since, it is circular linked list tail will point to head.
            $this->tail->next = $this->head;
        }
    }
    //Displays all the nodes in the list
    function display() {
        $current = $this->head;
        if($this->head == NULL) {
            echo "List is empty";
        }
        else {
            echo "Adding nodes to the end of the list: <br>";
             do{
                echo(" $current->data");
                $current = $current->next;
            }while($current != $this->head);
            echo "<br>";
        }
    }   
}
$cl = new CreateList();
//Adding 1 to the list
$cl->addAtEnd(1);
$cl->display();
//Adding 2 to the list
$cl->addAtEnd(2);
$cl->display();
//Adding 3 to the list
$cl->addAtEnd(3);
$cl->display();
//Adding 4 to the list
$cl->addAtEnd(4);
$cl->display();
?>
</body>
</html>

Output:

Adding nodes to the end of the list: 
1
Adding nodes to the end of the list: 
1 2
Adding nodes to the end of the list: 
1 2 3
Adding nodes to the end of the list: 
1 2 3 4

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