DSA: Doubly Linked List — Delete the first node
- First node will be deleted.
- Process:
- Check the head If its not null create a temp node, pointing to the head.
- Move the head to the next of head.
- Delete the temp node.
- If the head is not null make prev as null.
- Fig:
https://static.javatpoint.com/ds/images/deletion-in-doubly-linked-list-at-beginning.png
- Its 4-step process; eg :
<?php
//create node structure = data structure
class Node
{
public $data;
public $prev;
public $next;
}
// the algorithm
class LinkedList
{
public $head;
public function __construct()
{
$this->head;
}
//display link contents
public function display()
{
$temp = new Node();
$temp = $this->head;
if ($temp != null) {
echo “The list contains: “;
while ($temp != null) {
echo $temp->data . “ “;
$temp = $temp->next;
}
echo “\n”;
} else {
echo “The list is empty.\n”;
}
}
//method to add elements at the end of the list
public function addElements($newElement)
{
$newNode = new Node();
$newNode->data = $newElement;
$newNode->next = null;
$newNode->prev = null;
if ($this->head == null) {
$this->head = $newNode;
} else {
$temp = new Node();
$temp = $this->head;
if ($temp->next != null) {
$temp = $temp->next;
}
$temp->next = $newNode;
$newNode->prev = $temp;
}
}
//Delete the first node
public function delete_first()
{
//Check the head if its null or not
if ($this->head != null) {
//1.If head is not null create a temp node pointing to the head
$temp = $this->head;
//2.Move the head node to the next of the head list
$this->head = $this->head->next;
//3.Delete the temp node
$temp = null;
//4.If the head is not null, then make the prev of the new head as null
if ($this->head != null) {
$this->head->prev = null;
}
}
}
};
//Write test for the code
//Create instance of the linked_list
$myLinkedList = new LinkedList();
$myLinkedList->addElements(10);
$myLinkedList->addElements(11);
$myLinkedList->addElements(13);
$myLinkedList->addElements(12);
//To print this list
$myLinkedList->display();
echo “<br>”;
$myLinkedList->delete_first();
$myLinkedList->display();
?>
