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Program to create a doubly linked list of n nodes and display it in reverse order

belongs to collection: Doubly Linked List Programs

robaa
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2022-11-10
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Explanation

In this program, we create a doubly linked list, then reverse the list by reversing the direction of the list and print out the nodes.

Traverse through the list by swapping the previous pointer with next pointer of each node. Then, swap the position of head and tail node that is, head of the original list will become tail of new list and tail of the original list will become head of the new list. So, the reversed list will be:

Algorithm

  1. Define a Node class which represents a node in the list. It will have three properties: data, previous which will point to the previous node and next which will point to the next node.
  2. Define another class for creating a doubly linked list, and it has two nodes: head and tail. Initially, head and tail will point to null.
  3. addNode() will add node to the list:
    1. It first checks whether the head is null, then it will insert the node as the head.
    2. Both head and tail will point to a newly added node.
    3. Head's previous pointer will point to null and tail's next pointer will point to null.
    4. If the head is not null, the new node will be inserted at the end of the list such that new node's previous pointer will point to tail.
    5. The new node will become the new tail. Tail's next pointer will point to null.
  4. reverse() will reverse the given doubly linked list.
    1. Define a node current which will initially point to head.
    2. Traverse through the list by making current to point to current.next in each iteration till current points to null.
    3. In each iteration, swap previous and next pointer of each node to reverse the direction of the list.
    4. In the end, swap the position of head and tail.
  5. display() will show all the nodes present in the list.
    1. Define a new node 'current' that will point to the head.
    2. Print current.data till current points to null.
    3. Current will point to the next node in the list in each iteration.

Input:

 

#Add nodes to the list  

dList.addNode(1);  

dList.addNode(2);  

dList.addNode(3);  

dList.addNode(4);  

dList.addNode(5);   

Output:

Original List: 1 2 3 4 5 
Reversed List: 5 4 3 2 1
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All Answers

robaa
2022-11-10
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Python

#Represent a node of doubly linked list  
class Node:  
    def __init__(self,data):  
        self.data = data;  
        self.previous = None;  
        self.next = None;  
          
class ReverseList:  
    #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;  
              
    #reverse() will reverse the doubly linked list  
    def reverse(self):  
        #Node current will point to head  
        current = self.head;  
          
        #Swap the previous and next pointers of each node to reverse the direction of the list  
        while(current != None):  
            temp = current.next;  
            current.next = current.previous;  
            current.previous = temp;  
            current = current.previous;  
        #Swap the head and tail pointers.  
        temp = self.head;  
        self.head = self.tail;  
        self.tail = temp;  
          
    #display() will print out the elements 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;  
              
dList = ReverseList();  
#Add nodes to the list  
dList.addNode(1);  
dList.addNode(2);  
dList.addNode(3);  
dList.addNode(4);  
dList.addNode(5);  
   
print("Original List: ");  
dList.display();  
   
#Reverse the given list  
dList.reverse();  
   
#Displays the reversed list  
print("\nReversed List: ");  
dList.display();

 

Output:

Original List: 
1 2 3 4 5 
Reversed List: 
5 4 3 2 1

 

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;  
    }  
}  
   
//reverse() will reverse the doubly linked list  
void reverse() {  
    //Node current will point to head  
    struct node *current = head, *temp = NULL;  
      
    //Swap the previous and next pointers of each node to reverse the direction of the list  
    while(current != NULL) {  
        temp = current->next;  
        current->next = current->previous;  
        current->previous = temp;  
        current = current->previous;  
    }  
    //Swap the head and tail pointers.  
    temp = head;  
    head = tail;  
    tail = temp;  
}  
   
//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;  
    }  
}  
   
int main()  
{  
    //Add nodes to the list  
    addNode(1);  
    addNode(2);  
    addNode(3);  
    addNode(4);  
    addNode(5);  
      
    printf("Original List: \n");  
    display();  
      
    //Reverse the given list  
    reverse();  
      
    //Displays the reversed list  
    printf("\nReversed List: \n");  
    display();  
   
    return 0;  
}

 

Output:

Original List: 
1 2 3 4 5 
Reversed List: 
5 4 3 2 1

 

JAVA

public class ReverseList {  
      
    //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;  
        }  
    }  
      
    //reverse() will reverse the doubly linked list  
    public void reverse() {  
        //Node current will point to head  
        Node current = head, temp = null;  
          
        //Swap the previous and next pointers of each node to reverse the direction of the list  
        while(current != null) {  
            temp = current.next;  
            current.next = current.previous;  
            current.previous = temp;  
            current = current.previous;  
        }  
        //Swap the head and tail pointers.  
        temp = head;  
        head = tail;  
        tail = temp;  
    }  
      
    //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;  
        }  
          
        while(current != null) {  
            //Prints each node by incrementing the pointer.  
  
            System.out.print(current.data + " ");  
            current = current.next;  
        }  
    }  
      
    public static void main(String[] args) {  
          
        ReverseList dList = new ReverseList();  
        //Add nodes to the list  
        dList.addNode(1);  
        dList.addNode(2);  
        dList.addNode(3);  
        dList.addNode(4);  
        dList.addNode(5);  
          
        System.out.println("Original List: ");  
        dList.display();  
          
        //Reverse the given list  
        dList.reverse();  
          
        //Displays the reversed list  
        System.out.println("\nReversed List: ");  
        dList.display();  
    }  
}

 

Output:

Original List: 
1 2 3 4 5 
Reversed List: 
5 4 3 2 1

 

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 ReverseList<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;  
                }  
            }  
              
            //reverse() will reverse the doubly linked list  
            public void reverse() {  
                //Node current will point to head  
                Node<T> current = head, temp = null;  
   
                //Swap the previous and next pointers of each node to reverse the direction of the list  
                while(current != null) {  
                    temp = current.next;  
                    current.next = current.previous;  
                    current.previous = temp;  
                    current = current.previous;  
                }  
                //Swap the head and tail pointers.  
                temp = head;  
                head = tail;  
                tail = temp;  
            }  
              
            //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;  
                }  
            }  
        }  
          
        public static void Main()  
        {  
            ReverseList<int> dList = new ReverseList<int>();  
            //Add nodes to the list  
            dList.addNode(1);  
            dList.addNode(2);  
            dList.addNode(3);  
            dList.addNode(4);  
            dList.addNode(5);  
   
            Console.WriteLine("Original List: ");  
            dList.display();  
   
            //Reverse the given list  
            dList.reverse();  
   
            //Displays the reversed list  
            Console.WriteLine("\nReversed List: ");  
            dList.display();  
        }      
    }  
}

 

Output:

Original List: 
1 2 3 4 5 
Reversed List: 
5 4 3 2 1

 

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 ReverseList{  
    //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;  
        }  
    }  
      
    //reverse() will reverse the doubly linked list  
    function reverse() {  
        //Node current will point to head  
        $current = $this->head;  
          
        //Swap the previous and next pointers of each node to reverse the direction of the list  
        while($current != NULL) {  
            $temp = $current->next;  
            $current->next = $current->previous;  
            $current->previous = $temp;  
            $current = $current->previous;  
        }  
        //Swap the head and tail pointers.  
        $temp = $this->head;  
        $this->head = $this->tail;  
        $this->tail = $temp;  
    }  
      
    //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;  
        }  
    }  
}  
      
$dList = new ReverseList();  
//Add nodes to the list  
$dList->addNode(1);  
$dList->addNode(2);  
$dList->addNode(3);  
$dList->addNode(4);  
$dList->addNode(5);  
   
print("Original List: <br>");  
$dList->display();  
   
//Reverse the given list  
$dList->reverse();  
   
//Displays the reversed list  
print("<br>Reversed List: <br>");  
$dList->display();  
?>  
</body>  
</html>

 

Output:

Original List: 
1 2 3 4 5 
Reversed List: 
5 4 3 2 1

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Doubly Linked List Programs
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