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

Program to Delete a New Node From the Beginning of the Doubly Linked List on fibonacci, factorial, prime, armstrong, swap, reverse, search, sort, stack, queue, array, linkedlist, tree, graph etc.

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

### Explanation

In this program, we will create a doubly linked list and delete a node from the beginning of the list. If the list is empty, print the message "List is empty". If the list is not empty, we will make the head to point to next node in the list then; we will delete the first node.

Consider the above example, new was the head of the list. Make head to point to next node in the list. Now, node 1 will become the new head of the list thus, deleting node new.

### 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. deleteFromStart() will delete a node from the beginning 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, the head will point to next node in the list and delete the old head node.
4. 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 DeleteStart:
def __init__(self):
self.tail = None;

#Create a new node
newNode = Node(data);

#If list is empty
#Both head and tail will point to newNode
#head's previous will point to 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;

#deleteFromStart() will delete a node from the beginning of the list
def deleteFromStart(self):
#Checks whether list is empty
return;
else:
#Checks whether the list contains only one element
#head will point to next node in the list

#If the list contains only one element
#then, it will remove the node, and now both head and tail will point to None

else:

#display() will print out the nodes of the list
def display(self):
#Node current will point to head
print("List is empty");
return;
while(current != None):
#Prints each node by incrementing pointer.
print(current.data),
current = current.next;
print();

dList = DeleteStart();

#Printing original list
print("Original List: ");
dList.display();
dList.deleteFromStart();
#Printing updated list
print("Updated List: ");
dList.display();
```

Output:

```Original List:
1 2 3 4 5
Updated List:
2 3 4 5
Updated List:
3 4 5
Updated List:
4 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;
};

struct node *head, *tail = NULL;

//Create a new node
struct node *newNode = (struct node*)malloc(sizeof(struct node));
newNode->data = data;

//If list is empty
//Both head and tail will point to newNode
//head's previous will point to 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;
}
}

//deleteFromStart() will delete a node from the beginning of the list
void deleteFromStart() {
//Checks whether list is empty
return;
}
else {
//Checks whether the list contains only one element
//head will point to next node in the list
}
//If the list contains only one element
//then, it will remove node and now both head and tail will point to NULL
else {
}
}
}

//display() will print out the nodes of the list
void display() {
//Node current will point to head
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()
{

//Printing original list
printf("Original List: \n");
display();
deleteFromStart();
//Printing updated list
printf("Updated List: \n");
display();
}

return 0;
}
```

Output:

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

### JAVA

```public class DeleteStart {

//Represent a node of the doubly linked list

class Node{
int data;
Node previous;
Node next;

public Node(int data) {
this.data = data;
}
}

//Create a new node
Node newNode = new Node(data);

//If list is empty
//Both head and tail will point to newNode
//head's previous will point to 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;
}
}

//deleteFromStart() will delete a node from the beginning of the list
public void deleteFromStart() {
//Checks whether list is empty
return;
}
else {
//Checks whether the list contains only one element
//head will point to next node in the list
}
//If the list contains only one element
//then, it will remove node and now both head and tail will point to null
else {
}
}
}

//display() will print out the nodes of the list
public void display() {
//Node current will point to head
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) {

DeleteStart dList = new DeleteStart();

//Printing original list
System.out.println("Original List: ");
dList.display();
dList.deleteFromStart();
//Printing updated list
System.out.println("Updated List: ");
dList.display();
}
}
}
```

Output:

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

### C#

``` using System;
{
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 DeleteStart<T>{
public Node<T> tail = null;

//Create a new node
Node<T> newNode = new Node<T>(data);

//If list is empty
//Both head and tail will point to newNode
//head's previous will point to 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;
}
}

//deleteFromStart() will delete a node from the beginning of the list
public void deleteFromStart() {
//Checks whether list is empty
return;
}
else {
//Checks whether the list contains only one element
//head will point to next node in the list
}
//If the list contains only one element
//then, it will remove node and now both head and tail will point to null
else {
}
}
}

//display() will print out the nodes of the list
public void display() {
//Node current will point to head
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()
{
DeleteStart<int> dList = new DeleteStart<int>();

//Printing original list
Console.WriteLine("Original List: ");
dList.display();
dList.deleteFromStart();
//Printing updated list
Console.WriteLine("Updated List: ");
dList.display();
}
}
}
}
```

Output:

```Original List:
1 2 3 4 5
Updated List:
2 3 4 5
Updated List:
3 4 5
Updated List:
4 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 DeleteStart{
public \$tail;
function __construct(){
\$this->tail = NULL;
}

//Create a new node
\$newNode = new Node(\$data);

//If list is empty
//Both head and tail will point to newNode
//head's previous will point to 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;
}
}

//deleteFromStart() will delete a node from the beginning of the list
function deleteFromStart() {
//Checks whether list is empty
return;
}
else {
//Checks whether the list contains only one element
//head will point to next node in the list
}
//If the list contains only one element
//then, it will remove node and now both head and tail will point to NULL
else {
}
}
}

//display() will print out the nodes of the list
function display() {
//Node current will point to head
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 DeleteStart();

//Printing original list
print("Original List: <br>");
\$dList->display();
\$dList->deleteFromStart();
//Printing updated list
print("Updated List: <br>");
\$dList->display();
}
?>
</body>
</html>
```

Output:

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

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