Program to Create and Display a Circular Linked List

Q. Program to create and display a circular linked list.

Explanation

In this program, we will create a circular linked list and print all the nodes present in the list.

Circular Linked List:

The circular linked list is a kind of linked list. First thing first, the node is an element of the list, and it has two parts that are, data and next. Data represents the data stored in the node and next is the pointer that will point to next node. Head will point to the first element of the list, and tail will point to the last element in the list. In the simple linked list, all the nodes will point to their next element and tail will point to null.

The circular linked list is the collection of nodes in which tail node also point back to head node. The diagram shown below depicts a circular linked list. Node A represents head and node D represents tail. So, in this list, A is pointing to B, B is pointing to C and C is pointing to D but what makes it circular is that node D is pointing back to node A.

Program to create and display a circular linked list

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: add() and display() .
add() will add the node to the list:
1. It first checks whether the head is null, then it will insert the node as the head.
2. Both head and tail will point to the newly added node.
3. If the head is not null, the new node will be the new tail, and the new tail will point to the head as it is a circular linked list.
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
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 the new node at the end of the list.
  def add(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("Nodes of the circular linked list: ");
        #Prints each node by incrementing pointer.
        print(current.data),
        while(current.next != self.head):
            current = current.next;
            print(current.data),
 
 
class CircularLinkedList:
  cl = CreateList();
  #Adds data to the list
  cl.add(1);
  cl.add(2);
  cl.add(3);
  cl.add(4);
  #Displays all the nodes present in the list
  cl.display();

Output:

Nodes of the circular linked 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 add(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("Nodes of the circular linked list: \n");
         do{
             //Prints each node by incrementing pointer.
            printf("%d ", current->data);
            current = current->next;
        }while(current != head);
        printf("\n");
    }
}
    
int main()
{
    //Adds data to the list
   add(1);
   add(2);
   add(3);
   add(4);
   //Displays all the nodes present in the list
   display();
   
   return 0;
}

Output:

Nodes of the circular linked list: 
1 2 3 4

JAVA

public class CreateList {
    //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 add(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 point 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("Nodes of the circular linked 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) {
        CreateList cl = new CreateList();
        //Adds data to the list
        cl.add(1);
        cl.add(2);
        cl.add(3);
        cl.add(4);
        //Displays all the nodes present in the list
        cl.display();
    }
}

Output:

Nodes of the circular linked 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 add(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;
                if(head == null){
                    Console.WriteLine("List is empty");
                }
                else{
                    //Prints each node by incrementing pointer.
                    Console.WriteLine("Nodes of the circular linked list: ");
                    Console.Write(" "+head.data);
                    for(current = head.next; current!= head; current= current.next){
                        Console.Write(" "+current.data);
                    }
                }    
            }
        }
        
        public static void Main()
        {
            
        CreateList<int> cl = new CreateList<int>();
        //Adds data to the list
        cl.add(1);
        cl.add(2);
        cl.add(3);
        cl.add(4);
        //Displays all the nodes present in the list
        cl.display();
        }    
    }
}

Output:

Nodes of the circular linked 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;
        $this->tail = NULL;
    }
    //This function will add the new node at the end of the list.
    function add($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 "Nodes of the circular linked list: <br>";
             do{
                //Prints each node by incrementing pointer.
                echo(" $current->data");
                $current = $current->next;
            }while($current != $this->head);
            echo "<br>";
        }
    }   
}
$cl = new CreateList();
//Adds data to the list
$cl->add(1);
$cl->add(2);
$cl->add(3);
$cl->add(4);
//Displays all the nodes present in the list
$cl->display();
?>
</body>
</html>

Output:

Nodes of the circular linked list: 
1 2 3 4

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