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Program to create and display a doubly linked list

belongs to collection: Doubly Linked List Programs

robaa
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2022-11-10
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Explanation

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

Doubly Linked List:

Doubly Linked List is a variation of the linked list. The linked list is a linear data structure which can be described as the collection of nodes. Nodes are connected through pointers. Each node contains two fields: data and pointer to the next field. The first node of the linked list is called the head, and the last node of the list is called the tail of the list.

One of the limitations of the singly linked list is that it can be traversed in only one direction that is forward. The doubly linked list has overcome this limitation by providing an additional pointer that points to the previous node. With the help of the previous pointer, the doubly linked list can be traversed in a backward direction thus making insertion and deletion operation easier to perform. So, a typical node in the doubly linked list consists of three fields:

Data represents the data value stored in the node.

Previous represents a pointer that points to the previous node.

Next represents a pointer that points to next node in the list.

Above picture represents a doubly linked list in which each node has two pointers to point to previous and next node respectively. Here, node 1 represents the head of the list. The previous pointer of the head node will always point to NULL. Next pointer of node one will point to node 2. Node 5 represents the tail of the list whose previous pointer will point to node 4, and next will point to NULL.

Algorithm

  1. Define a Node class which represents a node in the list. It will have three properties: data, previous which will point to the previous node and next which will point to the next node.
  2. Define another class for creating a doubly linked list, and it has two nodes: head and tail. Initially, head and tail will point to null.
  3. addNode() will add 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 a newly added node.
    3. Head's previous pointer will point to null and tail's next pointer will point to null.
    4. If the head is not null, the new node will be inserted at the end of the list such that new node's previous pointer will point to tail.
    5. The new node will become the new tail. Tail's next pointer will point to null.
  4. 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 points to null.
    3. Current will point to the next node in the list in each iteration.

Input:

 

#Add nodes to the list  

dList.addNode(1);  

dList.addNode(2);  

dList.addNode(3);  

dList.addNode(4);  

dList.addNode(5);   

Output:

Nodes of doubly linked list: 1 2 3 4 5
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All Answers

robaa
2022-11-10
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Python

#Represent a node of doubly linked list  
class Node:  
    def __init__(self,data):  
        self.data = data;  
        self.previous = None;  
        self.next = None;  
          
class DoublyLinkedList:  
    #Represent the head and tail of the doubly linked list  
    def __init__(self):  
        self.head = None;  
        self.tail = None;  
          
    #addNode() will add a node to the list  
    def addNode(self, data):  
        #Create a new node  
        newNode = Node(data);  
          
        #If list is empty  
        if(self.head == None):  
            #Both head and tail will point to newNode  
            self.head = self.tail = newNode;  
            #head's previous will point to None  
            self.head.previous = None;  
            #tail's next will point to None, as it is the last node of the list  
            self.tail.next = None;  
        else:  
            #newNode will be added after tail such that tail's next will point to newNode  
            self.tail.next = newNode;  
            #newNode's previous will point to tail  
            newNode.previous = self.tail;  
            #newNode will become new tail  
            self.tail = newNode;  
            #As it is last node, tail's next will point to None  
            self.tail.next = None;  
              
    #display() will print out the nodes of the list  
    def display(self):  
        #Node current will point to head  
        current = self.head;  
        if(self.head == None):  
            print("List is empty");  
            return;  
        print("Nodes of doubly linked list: ");  
        while(current != None):   
            #Prints each node by incrementing pointer.  
            print(current.data),;  
            current = current.next;  
              
dList = DoublyLinkedList();  
#Add nodes to the list  
dList.addNode(1);  
dList.addNode(2);  
dList.addNode(3);  
dList.addNode(4);  
dList.addNode(5);  
   
#Displays the nodes present in the list  
dList.display();

 

Output:

Nodes of doubly linked list: 
1 2 3 4 5

 

C

#include <stdio.h>  
   
//Represent a node of the doubly linked list  
  
struct node{  
    int data;  
    struct node *previous;  
    struct node *next;  
};      
   
//Represent the head and tail of the doubly linked list  
struct node *head, *tail = NULL;  
   
//addNode() will add a node to the list  
void addNode(int data) {  
    //Create a new node  
    struct node *newNode = (struct node*)malloc(sizeof(struct node));  
    newNode->data = data;  
      
    //If list is empty  
    if(head == NULL) {  
        //Both head and tail will point to newNode  
        head = tail = newNode;  
        //head's previous will point to NULL  
        head->previous = NULL;  
        //tail's next will point to NULL, as it is the last node of the list  
        tail->next = NULL;  
    }  
    else {  
        //newNode will be added after tail such that tail's next will point to newNode  
        tail->next = newNode;  
        //newNode's previous will point to tail  
        newNode->previous = tail;  
        //newNode will become new tail  
        tail = newNode;  
        //As it is last node, tail's next will point to NULL  
        tail->next = NULL;  
    }  
}  
   
//display() will print out the nodes of the list  
void display() {  
    //Node current will point to head  
    struct node *current = head;  
    if(head == NULL) {  
        printf("List is empty\n");  
        return;  
    }  
    printf("Nodes of doubly linked list: \n");  
    while(current != NULL) {  
        //Prints each node by incrementing pointer.  
        printf("%d ", current->data);  
        current = current->next;  
    }  
}  
   
int main()  
{  
    //Add nodes to the list  
    addNode(1);  
    addNode(2);  
    addNode(3);  
    addNode(4);  
    addNode(5);  
      
    //Displays the nodes present in the list  
    display();  
   
    return 0;  
    }

 

Output:

Nodes of doubly linked list: 
1 2 3 4 5

 

JAVA

public class DoublyLinkedList {  
      
    //Represent a node of the doubly linked list  
  
    class Node{  
        int data;  
        Node previous;  
        Node next;  
          
        public Node(int data) {  
            this.data = data;  
        }  
    }  
      
    //Represent the head and tail of the doubly linked list  
    Node head, tail = null;  
      
    //addNode() will add a node to the list  
    public void addNode(int data) {  
        //Create a new node  
        Node newNode = new Node(data);  
          
        //If list is empty  
        if(head == null) {  
            //Both head and tail will point to newNode  
            head = tail = newNode;  
            //head's previous will point to null  
            head.previous = null;  
            //tail's next will point to null, as it is the last node of the list  
            tail.next = null;  
        }  
        else {  
            //newNode will be added after tail such that tail's next will point to newNode  
            tail.next = newNode;  
            //newNode's previous will point to tail  
            newNode.previous = tail;  
            //newNode will become new tail  
            tail = newNode;  
            //As it is last node, tail's next will point to null  
            tail.next = null;  
        }  
    }  
      
    //display() will print out the nodes of the list  
    public void display() {  
        //Node current will point to head  
        Node current = head;  
        if(head == null) {  
            System.out.println("List is empty");  
            return;  
        }  
        System.out.println("Nodes of doubly linked list: ");  
        while(current != null) {  
            //Prints each node by incrementing the pointer.  
  
            System.out.print(current.data + " ");  
            current = current.next;  
        }  
    }  
      
    public static void main(String[] args) {  
          
        DoublyLinkedList dList = new DoublyLinkedList();  
        //Add nodes to the list  
        dList.addNode(1);  
        dList.addNode(2);  
        dList.addNode(3);  
        dList.addNode(4);  
        dList.addNode(5);  
          
        //Displays the nodes present in the list  
        dList.display();  
    }  
}

 

Output:

Nodes of doubly linked list: 
1 2 3 4 5

 

C#

using System;   
namespace DoublyLinkedList   
{                       
    public class Program  
    {  
        //Represent a node of the doubly linked list  
  
        public class Node<T>{  
            public T data;  
            public Node<T> previous;  
            public Node<T> next;  
              
            public Node(T value) {  
                data = value;  
            }  
        }  
          
        public class DoublyLinkedList<T>{  
            //Represent the head and tail of the doubly linked list  
            protected Node<T> head = null;               
             protected Node<T> tail = null;  
              
            //addNode() will add a node to the list  
            public void addNode(T data) {  
                //Create a new node  
                Node<T> newNode = new Node<T>(data);  
   
                //If list is empty  
                if(head == null) {  
                    //Both head and tail will point to newNode  
                    head = tail = newNode;  
                    //head's previous will point to null  
                    head.previous = null;  
                    //tail's next will point to null, as it is the last node of the list  
                    tail.next = null;  
                }  
                else {  
                    //newNode will be added after tail such that tail's next will point to newNode  
                    tail.next = newNode;  
                    //newNode's previous will point to tail  
                    newNode.previous = tail;  
                    //newNode will become new tail  
                    tail = newNode;  
                    //As it is last node, tail's next will point to null  
                    tail.next = null;  
                }  
            }  
      
            //display() will print out the nodes of the list  
            public void display() {  
                //Node current will point to head  
                Node<T> current = head;  
                if(head == null) {  
                    Console.WriteLine("List is empty");  
                    return;  
                }  
                Console.WriteLine("Nodes of doubly linked list: ");  
                while(current != null) {  
                    //Prints each node by incrementing the pointer.  
  
                    Console.Write(current.data + " ");  
                    current = current.next;  
                }  
            }  
        }  
          
        public static void Main()  
        {  
            DoublyLinkedList<int> dList = new DoublyLinkedList<int>();  
            //Add nodes to the list  
            dList.addNode(1);  
            dList.addNode(2);  
            dList.addNode(3);  
            dList.addNode(4);  
            dList.addNode(5);  
   
            //Displays the nodes present in the list  
            dList.display();  
        }      
    }  
}

 

Output:

Nodes of doubly linked list: 
1 2 3 4 5

 

PHP

 <!DOCTYPE html>  
<html>  
<body>  
<?php  
//Represent a node of doubly linked list  
class Node{  
    public $data;  
    public $previous;  
    public $next;  
      
    function __construct($data){  
        $this->data = $data;  
    }  
}  
class DoublyLinkedList{  
    //Represent the head and tail of the doubly linked list  
    public $head;  
    public $tail;  
    function __construct(){  
        $this->head = NULL;  
        $this->tail = NULL;  
    }  
      
    //addNode() will add a node to the list  
    function addNode($data){  
        //Create a new node  
        $newNode = new Node($data);  
          
        //If list is empty  
        if($this->head == NULL) {  
            //Both head and tail will point to newNode  
            $this->head = $this->tail = $newNode;  
            //head's previous will point to NULL  
            $this->head->previous = NULL;  
            //tail's next will point to NULL, as it is the last node of the list  
            $this->tail->next = NULL;  
        }  
        else {  
            //newNode will be added after tail such that tail's next will point to newNode  
            $this->tail->next = $newNode;  
            //newNode's previous will point to tail  
            $newNode->previous = $this->tail;  
            //newNode will become new tail  
            $this->tail = $newNode;  
            //As it is last node, tail's next will point to NULL  
            $this->tail->next = NULL;  
        }  
    }  
      
    //display() will print out the nodes of the list  
    function display() {  
        //Node current will point to head  
        $current = $this->head;  
        if($this->head == NULL) {  
            print("List is empty <br>");  
            return;  
        }  
        print("Nodes of doubly linked list: <br>");  
        while($current != NULL) {  
            //Prints each node by incrementing pointer.  
            print($current->data . " ");  
            $current = $current->next;  
        }  
    }  
}  
      
$dList = new DoublyLinkedList();  
//Add nodes to the list  
$dList->addNode(1);  
$dList->addNode(2);  
$dList->addNode(3);  
$dList->addNode(4);  
$dList->addNode(5);  
   
//Displays the nodes present in the list  
$dList->display();  
?>  
</body>  
</html>

 

Output:

Nodes of doubly linked list: 
1 2 3 4 5

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Doubly Linked List Programs
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