Q:

Program to create a doubly linked list of n nodes and count the number of nodes

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 count the number of nodes present in the list. To count the node, we traverse through the list by incrementing the counter by 1.

What count of nodes presents above doubly linked list is 5.

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. countNodes() will count the number of nodes present in the list.
    1. Define a variable counter and new node current which will point to the head node.
    2. Traverse through the list to count the nodes by making the current node to point to next node in the list till current point to null.
    3. Increment the counter by 1.
  5. 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 
Count of nodes present in the list: 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 CountList:  
    #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;  
              
    #countNodes() will count the nodes present in the list  
    def countNodes(self):  
        counter = 0;  
        #Node current will point to head  
        current = self.head;  
          
        while(current != None):  
            #Increment the counter by 1 for each node  
            counter = counter + 1;  
            current = current.next;  
        return counter;  
              
    #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 = CountList();  
#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();  
   
#Counts the nodes present in the given list  
print("\nCount of nodes present in the list: " + str(dList.countNodes()));

 

Output:

Nodes of doubly linked list: 
1 2 3 4 5 
Count of nodes present in the list: 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;  
    }  
}  
   
//countNodes() will count the nodes present in the list  
int countNodes() {  
    int counter = 0;  
    //Node current will point to head  
    struct node *current = head;  
      
    while(current != NULL) {  
        //Increment the counter by 1 for each node  
        counter++;  
        current = current->next;  
    }  
    return counter;  
}  
      
//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();  
      
    //Counts the nodes present in the given list  
    printf("\nCount of nodes present in the list: %d", countNodes());  
   
    return 0;  
}

 

Output:

Nodes of doubly linked list: 
1 2 3 4 5 
Count of nodes present in the list: 5

 

JAVA

public class CountList {  
      
    //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;  
        }  
    }  
      
    //countNodes() will count the nodes present in the list  
    public int countNodes() {  
        int counter = 0;  
        //Node current will point to head  
        Node current = head;  
          
        while(current != null) {  
            //Increment the counter by 1 for each node  
            counter++;  
            current = current.next;  
        }  
        return counter;  
    }  
      
    //display() will print out the elements 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) {  
          
        CountList dList = new CountList();  
        //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();  
          
        //Counts the nodes present in the given list  
        System.out.println("\nCount of nodes present in the list: " + dList.countNodes());  
    }  
}

 

Output:

Nodes of doubly linked list: 
1 2 3 4 5 
Count of nodes present in the list: 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 CountList<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;  
                }  
            }  
              
            //countNodes() will count the nodes present in the list  
            public int countNodes() {  
                int counter = 0;  
                //Node current will point to head  
                Node<T> current = head;  
   
                while(current != null) {  
                    //Increment the counter by 1 for each node  
                    counter++;  
                    current = current.next;  
                }  
                return counter;  
            }  
              
            //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()  
        {  
            CountList<int> dList = new CountList<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();  
   
            //Counts the nodes present in the given list  
            Console.WriteLine("\nCount of nodes present in the list: " + dList.countNodes());  
        }      
    }  
}

 

Output:

Nodes of doubly linked list: 
1 2 3 4 5 
Count of nodes present in the list: 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 CountList{  
    //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;  
        }  
    }  
      
    //countNodes() will count the nodes present in the list  
    function countNodes() {  
        $counter = 0;  
        //Node current will point to head  
        $current = $this->head;  
          
        while($current != NULL) {  
            //Increment the counter by 1 for each node  
            $counter++;  
            $current = $current->next;  
        }  
        return $counter;  
    }  
      
    //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 CountList();  
//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();  
   
//Counts the nodes present in the given list  
print("<br>Count of nodes present in the list: " . $dList->countNodes());  
?>  
</body>  
</html>

 

Output:

Nodes of doubly linked list: 
1 2 3 4 5 
Count of nodes present in the list: 5

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Doubly Linked List Programs
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