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Q. Program to insert a new node at the middle of doubly linked list.ExplanationIn this program, we create a doubly linked list and insert a new node in the middle of list. If list is empty, both head and tail will point to new node. If list is not empty, then we will calculate the size of the list and divide it by 2 to get the midpoint of the list where new node needs to be inserted. Consider the above diagram; a new node needs to be added to the middle of the list. First, we calculate the size which in this case is 4. So, to get the midpoint, we divide it by 2 and store it in a variable mid. Node current will point to head. First, we iterate through the list until current points to mid position. Define another node temp which point to node next to current. Insert the new node between current and temp 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 InsertMid: #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; #addInMid() will add a node to the middle of the list def addInMid(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 point to None, as it is the last node of the list self.tail.next = None; 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; #Node temp will point to node next to current temp = current.next; temp.previous = current; #newNode will be added between current and temp current.next = newNode; newNode.previous = current; newNode.next = temp; temp.previous = newNode; 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 = InsertMid(); #Add nodes to the list dList.addNode(1); dList.addNode(2); print("Original list: "); dList.display(); #Adding node '3' in the middle dList.addInMid(3); print( "Updated List: "); dList.display(); #Adding node '4' in the middle dList.addInMid(4); print("Updated List: "); dList.display(); #Adding node '5' in the middle dList.addInMid(5); print("Updated List: "); dList.display(); Output: Original list: 1 2 Updated List: 1 3 2 Updated List: 1 3 4 2 Updated List: 1 3 5 4 2 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++; } //addInMid() will add a node to the middle of the list void addInMid(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 point to NULL, as it is the last node of the list tail>next = NULL; } else { //current will point to head struct node *current = head, *temp = NULL; //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; } //Node temp will point to node next to current temp = current>next; temp>previous = current; //newNode will be added between current and temp current>next = newNode; newNode>previous = current; newNode>next = temp; temp>previous = newNode; } 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); printf("Original list: \n"); display(); //Adding node '3' in the middle addInMid(3); printf( "Updated List: \n"); display(); //Adding node '4' in the middle addInMid(4); printf("Updated List: \n"); display(); //Adding node '5' in the middle addInMid(5); printf("Updated List: \n"); display(); return 0; } Output: Original list: 1 2 Updated List: 1 3 2 Updated List: 1 3 4 2 Updated List: 1 3 5 4 2 JAVApublic class InsertMid { //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++; } //addInMid() will add a node to the middle of the list public void addInMid(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 point to null, as it is the last node of the list tail.next = null; } else { //current will point to head Node current = head, temp = null; //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; } //Node temp will point to node next to current temp = current.next; temp.previous = current; //newNode will be added between current and temp current.next = newNode; newNode.previous = current; newNode.next = temp; temp.previous = newNode; } 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) { InsertMid dList = new InsertMid(); //Add nodes to the list dList.addNode(1); dList.addNode(2); System.out.println("Original list: "); dList.display(); //Adding node '3' in the middle dList.addInMid(3); System.out.println( "Updated List: "); dList.display(); //Adding node '4' in the middle dList.addInMid(4); System.out.println("Updated List: "); dList.display(); //Adding node '5' in the middle dList.addInMid(5); System.out.println("Updated List: "); dList.display(); } } Output: Original list: 1 2 Updated List: 1 3 2 Updated List: 1 3 4 2 Updated List: 1 3 5 4 2 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 InsertMid<T>{ public int size = 0; //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; } //Size will count the number of nodes present in the list size++; } //addInMid() will add a node to the middle of the list public void addInMid(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 point to null, as it is the last node of the list tail.next = null; } else { //current will point to head Node<T> current = head, temp = null; //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; } //Node temp will point to node next to current temp = current.next; temp.previous = current; //newNode will be added between current and temp current.next = newNode; newNode.previous = current; newNode.next = temp; temp.previous = newNode; } 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() { InsertMid<int> dList = new InsertMid<int>(); //Add nodes to the list dList.addNode(1); dList.addNode(2); Console.WriteLine("Original list: "); dList.display(); //Adding node '3' in the middle dList.addInMid(3); Console.WriteLine( "Updated List: "); dList.display(); //Adding node '4' in the middle dList.addInMid(4); Console.WriteLine("Updated List: "); dList.display(); //Adding node '5' in the middle dList.addInMid(5); Console.WriteLine("Updated List: "); dList.display(); } } } Output: Original list: 1 2 Updated List: 1 3 2 Updated List: 1 3 4 2 Updated List: 1 3 5 4 2 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 InsertMid{ //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 $this>size++; } //addInMid() will add a node to the middle of the list function addInMid($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 point to NULL, as it is the last node of the list $this>tail>next = NULL; } else { //current will point to head $current = $this>head; $temp = NULL; //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; } //Node temp will point to node next to current $temp = $current>next; $temp>previous = $current; //newNode will be added between current and temp $current>next = $newNode; $newNode>previous = $current; $newNode>next = $temp; $temp>previous = $newNode; } $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 InsertMid(); //Add nodes to the list $dList>addNode(1); $dList>addNode(2); print("Original list: <br>"); $dList>display(); //Adding node '3' in the middle $dList>addInMid(3); print( "Updated List: <br>"); $dList>display(); //Adding node '4' in the middle $dList>addInMid(4); print("Updated List: <br>"); $dList>display(); //Adding node '5' in the middle $dList>addInMid(5); print("Updated List: <br>"); $dList>display(); ?> </body> </html> Output: Original list: 1 2 Updated List: 1 3 2 Updated List: 1 3 4 2 Updated List: 1 3 5 4 2
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