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Q. Program to delete a new node from the beginning of the doubly linked list.ExplanationIn this program, we will create a doubly linked list and delete a node from the beginning of the list. If the list is empty, print the message "List is empty". If the list is not empty, we will make the head to point to next node in the list then; we will delete the first node. Consider the above example, new was the head of the list. Make head to point to next node in the list. Now, node 1 will become the new head of the list thus, deleting node new. 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 DeleteStart: #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; #deleteFromStart() will delete a node from the beginning of the list def deleteFromStart(self): #Checks whether list is empty if(self.head == None): return; else: #Checks whether the list contains only one element if(self.head != self.tail): #head will point to next node in the list self.head = self.head.next; #Previous node to current head will be made None self.head.previous = None; #If the list contains only one element #then, it will remove the node, and now both head and tail will point to None else: self.head = self.tail = 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; while(current != None): #Prints each node by incrementing pointer. print(current.data), current = current.next; print(); dList = DeleteStart(); #Add nodes to the list dList.addNode(1); dList.addNode(2); dList.addNode(3); dList.addNode(4); dList.addNode(5); #Printing original list print("Original List: "); dList.display(); while(dList.head != None): dList.deleteFromStart(); #Printing updated list print("Updated List: "); dList.display(); Output: Original List: 1 2 3 4 5 Updated List: 2 3 4 5 Updated List: 3 4 5 Updated List: 4 5 Updated List: 5 Updated List: List is empty 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; } } //deleteFromStart() will delete a node from the beginning of the list void deleteFromStart() { //Checks whether list is empty if(head == NULL) { return; } else { //Checks whether the list contains only one element if(head != tail) { //head will point to next node in the list head = head>next; //Previous node to current head will be made NULL head>previous = NULL; } //If the list contains only one element //then, it will remove node and now both head and tail will point to NULL else { head = tail = 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; } while(current != NULL) { //Prints each node by incrementing pointer. printf("%d ",current>data); current = current>next; } printf("\n"); } int main() { //Add nodes to the list addNode(1); addNode(2); addNode(3); addNode(4); addNode(5); //Printing original list printf("Original List: \n"); display(); while(head != NULL) { deleteFromStart(); //Printing updated list printf("Updated List: \n"); display(); } return 0; } Output: Original List: 1 2 3 4 5 Updated List: 2 3 4 5 Updated List: 3 4 5 Updated List: 4 5 Updated List: 5 Updated List: List is empty JAVApublic class DeleteStart { //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; } } //deleteFromStart() will delete a node from the beginning of the list public void deleteFromStart() { //Checks whether list is empty if(head == null) { return; } else { //Checks whether the list contains only one element if(head != tail) { //head will point to next node in the list head = head.next; //Previous node to current head will be made null head.previous = null; } //If the list contains only one element //then, it will remove node and now both head and tail will point to null else { head = tail = 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; } while(current != null) { //Prints each node by incrementing the pointer. System.out.print(current.data + " "); current = current.next; } System.out.println(); } public static void main(String[] args) { DeleteStart dList = new DeleteStart(); //Add nodes to the list dList.addNode(1); dList.addNode(2); dList.addNode(3); dList.addNode(4); dList.addNode(5); //Printing original list System.out.println("Original List: "); dList.display(); while(dList.head != null) { dList.deleteFromStart(); //Printing updated list System.out.println("Updated List: "); dList.display(); } } } Output: Original List: 1 2 3 4 5 Updated List: 2 3 4 5 Updated List: 3 4 5 Updated List: 4 5 Updated List: 5 Updated List: List is empty 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 DeleteStart<T>{ //Represent the head and tail of the doubly linked list public Node<T> head = null; public 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; } } //deleteFromStart() will delete a node from the beginning of the list public void deleteFromStart() { //Checks whether list is empty if(head == null) { return; } else { //Checks whether the list contains only one element if(head != tail) { //head will point to next node in the list head = head.next; //Previous node to current head will be made null head.previous = null; } //If the list contains only one element //then, it will remove node and now both head and tail will point to null else { head = tail = 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; } while(current != null) { //Prints each node by incrementing the pointer. Console.Write(current.data + " "); current = current.next; } Console.WriteLine(); } } public static void Main() { DeleteStart<int> dList = new DeleteStart<int>(); //Add nodes to the list dList.addNode(1); dList.addNode(2); dList.addNode(3); dList.addNode(4); dList.addNode(5); //Printing original list Console.WriteLine("Original List: "); dList.display(); while(dList.head != null) { dList.deleteFromStart(); //Printing updated list Console.WriteLine("Updated List: "); dList.display(); } } } } Output: Original List: 1 2 3 4 5 Updated List: 2 3 4 5 Updated List: 3 4 5 Updated List: 4 5 Updated List: 5 Updated List: List is empty 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 DeleteStart{ //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 $this>tail>next = NULL; } } //deleteFromStart() will delete a node from the beginning of the list function deleteFromStart() { //Checks whether list is empty if($this>head == NULL) { return; } else { //Checks whether the list contains only one element if($this>head != $this>tail) { //head will point to next node in the list $this>head = $this>head>next; //Previous node to current head will be made NULL $this>head>previous = NULL; } //If the list contains only one element //then, it will remove node and now both head and tail will point to NULL else { $this>head = $this>tail = 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; } while($current != NULL) { //Prints each node by incrementing pointer. print($current>data . " "); $current = $current>next; } print("<br>"); } } $dList = new DeleteStart(); //Add nodes to the list $dList>addNode(1); $dList>addNode(2); $dList>addNode(3); $dList>addNode(4); $dList>addNode(5); //Printing original list print("Original List: <br>"); $dList>display(); while($dList>head != NULL) { $dList>deleteFromStart(); //Printing updated list print("Updated List: <br>"); $dList>display(); } ?> </body> </html> Output: Original List: 1 2 3 4 5 Updated List: 2 3 4 5 Updated List: 3 4 5 Updated List: 4 5 Updated List: 5 Updated List: List is empty
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