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Q. Program to create a doubly linked list of n nodes and count the number of nodes.ExplanationIn 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
SolutionPython#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 JAVApublic 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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