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Q. Program to remove duplicate elements from a doubly linked list.ExplanationIn this program, we will create a doubly linked list and remove the duplicate, if present, by traversing through the list. Original List: List after removing duplicates: In above list, node2 is repeated thrice, and node 3 is repeated twice. Current will point to head, and index will point to node next to current. Start traversing the list till a duplicate is found that is when current's data is equal to index's data. In above example, the first duplicate will be found at position 4. Assign index to another node temp. Connect index's previous node with index's next node. Delete temp which was pointing to duplicate node. This process will continue till all duplicates are removed. 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 RemoveDuplicate: #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; #removeDuplicateNode() will remove duplicate nodes from the list def removeDuplicateNode(self): #Checks whether list is empty if(self.head == None): return; else: #Initially, current will point to head node current = self.head; while(current != None): #index will point to node next to current index = current.next while(index != None): if(current.data == index.data): #Store the duplicate node in temp temp = index; #index's previous node will point to node next to index thus, removes the duplicate node index.previous.next = index.next; if(index.next != None): index.next.previous = index.previous; #Delete duplicate node by making temp to None temp = None; index = index.next; current = current.next; #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 = RemoveDuplicate(); #Add nodes to the list dList.addNode(1); dList.addNode(2); dList.addNode(3); dList.addNode(2); dList.addNode(2); dList.addNode(4); dList.addNode(5); dList.addNode(3); print("Originals list: "); dList.display(); #Removes duplicate nodes dList.removeDuplicateNode(); print("List after removing duplicates: "); dList.display(); Output: Originals list: 1 2 3 2 2 4 5 3 List after removing duplicates: 1 2 3 4 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; } } //removeDuplicateNode() will remove duplicate nodes from the list void removeDuplicateNode() { //Node current will point to head struct node *current, *index, *temp; //Checks whether list is empty if(head == NULL) { return; } else { //Initially, current will point to head node for(current = head; current != NULL; current = current>next) { //index will point to node next to current for(index = current>next; index != NULL; index = index>next) { if(current>data == index>data) { //Store the duplicate node in temp temp = index; //index's previous node will point to node next to index thus, removes the duplicate node index>previous>next = index>next; if(index>next != NULL) index>next>previous = index>previous; //Delete duplicate node by making temp to NULL temp = 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(2); addNode(2); addNode(4); addNode(5); addNode(3); printf("Originals list: \n"); display(); //Removes duplicate nodes removeDuplicateNode(); printf("List after removing duplicates: \n"); display(); return 0; } Output: Originals list: 1 2 3 2 2 4 5 3 List after removing duplicates: 1 2 3 4 5 JAVApublic class RemoveDuplicate { //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; } } //removeDuplicateNode() will remove duplicate nodes from the list public void removeDuplicateNode() { //Node current will point to head Node current, index, temp; //Checks whether list is empty if(head == null) { return; } else { //Initially, current will point to head node for(current = head; current != null; current = current.next) { //index will point to node next to current for(index = current.next; index != null; index = index.next) { if(current.data == index.data) { //Store the duplicate node in temp temp = index; //index's previous node will point to node next to index thus, removes the duplicate node index.previous.next = index.next; if(index.next != null) index.next.previous = index.previous; //Delete duplicate node by making temp to null temp = 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) { RemoveDuplicate dList = new RemoveDuplicate(); //Add nodes to the list dList.addNode(1); dList.addNode(2); dList.addNode(3); dList.addNode(2); dList.addNode(2); dList.addNode(4); dList.addNode(5); dList.addNode(3); System.out.println("Originals list: "); dList.display(); //Removes duplicate nodes dList.removeDuplicateNode(); System.out.println("List after removing duplicates: "); dList.display(); } } Output: Originals list: 1 2 3 2 2 4 5 3 List after removing duplicates: 1 2 3 4 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 RemoveDuplicate<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; } } //removeDuplicateNode() will remove duplicate nodes from the list public void removeDuplicateNode() { //Node current will point to head Node<T> current, index, temp; //Checks whether list is empty if(head == null) { return; } else { //Initially, current will point to head node for(current = head; current != null; current = current.next) { //index will point to node next to current for(index = current.next; index != null; index = index.next) { if(current.data.Equals(index.data)) { //Store the duplicate node in temp temp = index; //index's previous node will point to node next to index thus, removes the duplicate node index.previous.next = index.next; if(index.next != null) index.next.previous = index.previous; //Delete duplicate node by making temp to null temp = 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() { RemoveDuplicate<int> dList = new RemoveDuplicate<int>(); //Add nodes to the list dList.addNode(1); dList.addNode(2); dList.addNode(3); dList.addNode(2); dList.addNode(2); dList.addNode(4); dList.addNode(5); dList.addNode(3); Console.WriteLine("Originals list: "); dList.display(); //Removes duplicate nodes dList.removeDuplicateNode(); Console.WriteLine("List after removing duplicates: "); dList.display(); } } } Output: Originals list: 1 2 3 2 2 4 5 3 List after removing duplicates: 1 2 3 4 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 RemoveDuplicate{ //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 $this>tail>next = NULL; } } //removeDuplicateNode() will remove duplicate nodes from the list function removeDuplicateNode() { //Checks whether list is empty if($this>head == NULL) { return; } else { //Initially, current will point to head node for($current = $this>head; $current != NULL; $current = $current>next) { //index will point to node next to current for($index = $current>next; $index != NULL; $index = $index>next) { if($current>data == $index>data) { //Store the duplicate node in temp $temp = $index; //index's previous node will point to node next to index thus, removes the duplicate node $index>previous>next = $index>next; if($index>next != NULL) $index>next>previous = $index>previous; //Delete duplicate node by making temp to NULL $temp = 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 RemoveDuplicate(); //Add nodes to the list $dList>addNode(1); $dList>addNode(2); $dList>addNode(3); $dList>addNode(2); $dList>addNode(2); $dList>addNode(4); $dList>addNode(5); $dList>addNode(3); print("Originals list: <br>"); $dList>display(); //Removes duplicate nodes $dList>removeDuplicateNode(); print("List after removing duplicates: <br>"); $dList>display(); ?> </body> </html> Output: Originals list: 1 2 3 2 2 4 5 3 List after removing duplicates: 1 2 3 4 5
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