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Q. Program to delete a new node from the middle of the doubly linked list.ExplanationIn this program, we will create a doubly linked list and delete a node from the middle of the list. If the list is empty, display the message "List is empty". If the list is not empty, we will calculate the size of the list and then divide it by 2 to get the midpoint of the list. Current will point to head node. We will iterate through the list till mid?point is reached. Now current will point to the middle node. We delete middle node such that current's previous node will point to the current's next node. Consider the above example, midpoint of above list is 3. Iterate current from head to midpoint. Now, the current is pointing to mid node which needs to be deleted. In this case, node new is the middle node which needs to be deleted. New can be deleted by making node 2 (current's previous node) to point to node 3 (current's next node). Set current to null. 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 DeleteMid: #Represent the head and tail of the doubly linked list def __init__(self): self.head = None; self.tail = None; self.size = 0; #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; #Size will count the number of nodes present in the list self.size = self.size + 1; #deleteFromMid() will delete a node from middle of the list def deleteFromMid(self): #Checks whether list is empty if(self.head == None): return; else: #current will point to head current = self.head; #Store the mid position of the list mid = (self.size//2) if(self.size % 2 == 0) else((self.size+1)//2); #Iterate through list till current points to mid position for i in range(1, mid): current = current.next; #If middle node is head of the list if(current == self.head): self.head = current.next; #If middle node is tail of the list elif(current == self.tail): self.tail = self.tail.previous; else: current.previous.next = current.next; current.next.previous = current.previous; #Delete the middle node current = None; self.size = self.size  1; #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 = DeleteMid(); #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.deleteFromMid(); #Printing updated list print("Updated List: ") dList.display(); Output: Original List: 1 2 3 4 5 Updated List: 1 2 4 5 Updated List: 1 4 5 Updated List: 1 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; }; int size = 0; //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; } //Size will count the number of nodes present in the list size++; } //deleteFromMid() will delete a node from middle of the list void deleteFromMid() { //Checks whether list is empty if(head == NULL) { return; } else { //current will point to head struct node *current = head; //Store the mid position of the list int mid = (size % 2 == 0) ? (size/2) : ((size+1)/2); //Iterate through list till current points to mid position for(int i = 1; i < mid; i++){ current = current>next; } //If middle node is head of the list if(current == head) { head = current>next; } //If middle node is tail of the list else if(current == tail) { tail = tail>previous; } else { current>previous>next = current>next; current>next>previous = current>previous; } //Delete the middle node current = NULL; } size; } //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) { deleteFromMid(); //Printing updated list printf("Updated List: \n"); display(); } return 0; } Output: Original List: 1 2 3 4 5 Updated List: 1 2 4 5 Updated List: 1 4 5 Updated List: 1 5 Updated List: 5 Updated List: List is empty JAVApublic class DeleteMid { //Represent a node of the doubly linked list class Node{ int data; Node previous; Node next; public Node(int data) { this.data = data; } } public int size = 0; //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; } //Size will count the number of nodes present in the list size++; } //deleteFromMid() will delete a node from middle of the list public void deleteFromMid() { //Checks whether list is empty if(head == null) { return; } else { //current will point to head Node current = head; //Store the mid position of the list int mid = (size % 2 == 0) ? (size/2) : ((size+1)/2); //Iterate through list till current points to mid position for(int i = 1; i < mid; i++){ current = current.next; } //If middle node is head of the list if(current == head) { head = current.next; } //If middle node is tail of the list else if(current == tail) { tail = tail.previous; } else { current.previous.next = current.next; current.next.previous = current.previous; } //Delete the middle node current = null; } size; } //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) { DeleteMid dList = new DeleteMid(); //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.deleteFromMid(); //Printing updated list System.out.println("Updated List: "); dList.display(); } } } Output: Original List: 1 2 3 4 5 Updated List: 1 2 4 5 Updated List: 1 4 5 Updated List: 1 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 DeleteMid<T>{ public int size = 0; //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; } //Size will count the number of nodes present in the list size++; } //deleteFromMid() will delete a node from middle of the list public void deleteFromMid() { //Checks whether list is empty if(head == null) { return; } else { //current will point to head Node<T> current = head; //Store the mid position of the list int mid = (size % 2 == 0) ? (size/2) : ((size+1)/2); //Iterate through list till current points to mid position for(int i = 1; i < mid; i++){ current = current.next; } //If middle node is head of the list if(current == head) { head = current.next; } //If middle node is tail of the list else if(current == tail) { tail = tail.previous; } else { current.previous.next = current.next; current.next.previous = current.previous; } //Delete the middle node current = null; } size; } //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() { DeleteMid<int> dList = new DeleteMid<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.deleteFromMid(); //Printing updated list Console.WriteLine("Updated List: "); dList.display(); } } } } Output: Original List: 1 2 3 4 5 Updated List: 1 2 4 5 Updated List: 1 4 5 Updated List: 1 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 DeleteMid{ //Represent the head and tail of the doubly linked list public $head; public $tail; public $size; function __construct(){ $this>head = NULL; $this>tail = NULL; $this>size = 0; } //addNode() will add a node to the list function addNode($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; } //Size will count the number of nodes present in the list $this>size++; } //deleteFromMid() will delete a node from middle of the list function deleteFromMid() { //Checks whether list is empty if($this>head == NULL) { return; } else { //current will point to head $current = $this>head; //Store the mid position of the list $mid = ($this>size % 2 == 0) ? ($this>size/2) : (($this>size+1)/2); //Iterate through list till current points to mid position for($i = 1; $i < $mid; $i++){ $current = $current>next; } //If middle node is head of the list if($current == $this>head) { $this>head = $current>next; } //If middle node is tail of the list else if($current == $this>tail) { $this>tail = $this>tail>previous; } else { $current>previous>next = $current>next; $current>next>previous = $current>previous; } //Delete the middle node $current = NULL; } $this>size; } //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 DeleteMid(); //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>deleteFromMid(); //Printing updated list print("Updated List: <br>"); $dList>display(); } ?> </body> </html> Output: Original List: 1 2 3 4 5 Updated List: 1 2 4 5 Updated List: 1 4 5 Updated List: 1 5 Updated List: 5 Updated List: List is empty
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