Program to Delete a New Node From the End of the Doubly Linked List

Q. Program to delete a new node from the end of the doubly linked list.

Explanation

In this program, we will create a doubly linked list and delete a node from the end of the list. If the list is empty, print the message "List is empty". If the list is not empty, tail's previous node will become the new tail of the list thus, deleting the last node from the list.

Program to delete a new node from the end of the doubly linked list

In above example, node new was the tail of the list. Make tail's previous node that is, node 4 as the tail of the list. Node 4's next will point to null.

Algorithm

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.
Define another class for creating the doubly linked list, and it has two nodes: head and tail. Initially, head and tail will point to null.
deleteFromEnd() will delete a node from the end of the list:
1. It first checks whether the head is null (empty list) then, it will return from the function as there is no node present in the list.
2. If the list is not empty, it will check whether the list has only one node.
3. If the list has only one node, it will set both head and tail to null.
4. If the list has more than one node then, tail's previous node will become the new tail of the list.
5. This new tail will point to null thus, delete the last node of the list.
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.

Solution

Python

#Represent a node of doubly linked list
class Node:
    def __init__(self,data):
        self.data = data;
        self.previous = None;
        self.next = None;
        
class DeleteEnd:
    #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;
            
    #deleteFromEnd() will delete a node from the end of the list
    def deleteFromEnd(self):
        #Checks whether list is empty
        if(self.head == None):
            return;
        else:
            #Checks whether the list contains only one node
            if(self.head != self.tail):
                #Previous node to the tail will become new tail
                self.tail = self.tail.previous;
                #Node next to current tail will be made None
                self.tail.next = 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 = DeleteEnd();
#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.deleteFromEnd();
    #Printing updated list
    print("Updated List: ");
    dList.display();

Output:

Original List: 
1 2 3 4 5 
Updated List: 
1 2 3 4 
Updated List: 
1 2 3 
Updated List: 
1 2 
Updated List: 
1 
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;
    }
}
 
//deleteFromEnd() will delete a node from the end of the list
void deleteFromEnd() {
    //Checks whether list is empty
    if(head == NULL) {
        return;
    }
    else {
        //Checks whether the list contains only one node
        if(head != tail) {
            //Previous node to the tail will become new tail
            tail = tail->previous;
            //Node next to current tail will be made NULL
            tail->next = 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) {
        deleteFromEnd();
        //Printing updated list
        printf("Updated List: \n");
        display();
    }    
 
    return 0;
}

Output:

Original List: 
1 2 3 4 5 
Updated List: 
1 2 3 4 
Updated List: 
1 2 3 
Updated List: 
1 2 
Updated List: 
1 
Updated List: 
List is empty

JAVA

public class DeleteEnd {
    
    //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;
        }
    }
    
    //deleteFromEnd() will delete a node from the end of the list
    public void deleteFromEnd() {
        //Checks whether list is empty
        if(head == null) {
            return;
        }
        else {
            //Checks whether the list contains only one node
            if(head != tail) {
                //Previous node to the tail will become new tail
                tail = tail.previous;
                //Node next to current tail will be made null
                tail.next = 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) {
        
        DeleteEnd dList = new DeleteEnd();
        //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.deleteFromEnd();
            //Printing updated list
            System.out.println("Updated List: ");
            dList.display();
        }    
    }
}

Output:

Original List: 
1 2 3 4 5 
Updated List: 
1 2 3 4 
Updated List: 
1 2 3 
Updated List: 
1 2 
Updated List: 
1 
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 DeleteEnd<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;
                }
            }
    
            //deleteFromEnd() will delete a node from the end of the list
            public void deleteFromEnd() {
                //Checks whether list is empty
                if(head == null) {
                    return;
                }
                else {
                    //Checks whether the list contains only one node
                    if(head != tail) {
                        //Previous node to the tail will become new tail
                        tail = tail.previous;
                        //Node next to current tail will be made null
                        tail.next = 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()
        {
            DeleteEnd<int> dList = new DeleteEnd<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.deleteFromEnd();
                //Printing updated list
                Console.WriteLine("Updated List: ");
                dList.display();
            }    
        }    
    }
}

Output:

Original List: 
1 2 3 4 5 
Updated List: 
1 2 3 4 
Updated List: 
1 2 3 
Updated List: 
1 2 
Updated List: 
1 
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 DeleteEnd{
    //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;
        }
    }
    
    //deleteFromEnd() will delete a node from the end of the list
    function deleteFromEnd() {
        //Checks whether list is empty
        if($this->head == NULL) {
            return;
        }
        else {
            //Checks whether the list contains only one node
            if($this->head != $this->tail) {
                //Previous node to the tail will become new tail
                $this->tail = $this->tail->previous;
                //Node next to current tail will be made null
                $this->tail->next = 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 DeleteEnd();
//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->deleteFromEnd();
    //Printing updated list
    print("Updated List: <br>");
    $dList->display();
}    
?>
</body>
</html>

Output:

Original List: 
1 2 3 4 5 
Updated List: 
1 2 3 4 
Updated List: 
1 2 3 
Updated List: 
1 2 
Updated List: 
1 
Updated List: 
List is empty

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