Basic operations in doubly linked list

basic-operations-in-doubly-linked-list-in-php.php

<?php

class Node
{
    public $value;
    public $next;
    public $prev;

    public function __construct($value)
    {
        $this->value = $value;
        $this->prev = null;
        $this->next = null;
    }
}

class DoublyLinkedList
{
    public $head;
    public $tail;
    public $length;

    public function __construct(public int $value)
    {
        $newNode = new Node($value);
        $this->head = $newNode;
        $this->tail = $newNode;
        $this->length = 1;
    }

    public function printAll()
    {
        $temp = $this->head;
        while ($temp != null) {
            echo $temp->value;
            $temp = $temp->next;
        }
        echo PHP_EOL;
    }

    public function append($value)
    {
        $newNode = new Node($value);

        if ($this->length == 0) {
            $this->head = $newNode;
            $this->tail = $newNode;
        } else {
            $newNode->prev = $this->tail;
            $this->tail->next = $newNode;
            $this->tail = $newNode;
        }

        $this->length++;
    }

    public function getNode($index)
    {
        if ($index < 0 || $index >= $this->length) {
            return null;
        }

        $temp = $this->head;
        for ($i = 0; $i < $index; $i++) {
            $temp = $temp->next;
        }

        return $temp;
    }

    public function getNodeOptimized($index)
    {
        if ($index < 0 || $index >= $this->length) {
            return null;
        }

        if ($index < $this->length / 2) {
            $temp = $this->head;
            for ($i = 0; $i < $index; $i++) {
                $temp = $temp->next;
            }
        } else {
            $temp = $this->tail;
            for ($i = $this->length - 1; $i > $index; $i--) {
                $temp = $temp->prev;
            }
        }

        return $temp;
    }

    public function setNode($index, $value)
    {
        $temp = $this->getNode($index);
        if ($temp) {
            $temp->value = $value;
        }
    }

    public function prepend($value)
    {
        $newNode = new Node($value);
        if ($this->length == 0) {
            $this->head = $newNode;
            $this->tail = $newNode;
        } else {
            $newNode->next = $this->head;
            $this->head->prev = $newNode;
            $this->head = $newNode;
        }

        $this->length++;
    }

    public function insert($index, $value)
    {
        if ($index < 0 || $index > $this->length) {
            return null;
        }

        if ($index == 0) {
            $this->prepend($value);
            return;
        }

        if ($index == $this->length) {
            $this->append($value);
            return;
        }

        $newNode = new Node($value);
        $before = $this->getNode($index - 1);
        $after = $before->next;

        $newNode->prev = $before;
        $newNode->next = $after;
        $before->next = $newNode;
        $after->prev = $newNode;

        $this->length++;
    }

    public function popFirst()
    {
        if ($this->length == 0) {
            return null;
        }

        $temp = $this->head;
        if ($this->length == 1) {
            $this->head = null;
            $this->tail = null;
        } else {
            $this->head = $this->head->next;
            $this->head->prev = null;
            $temp->next = null;
        }

        $this->length--;
        return $temp;
    }

    public function popLast()
    {
        if ($this->length == 0) {
            return null;
        }
        $temp = $this->tail;
        if ($this->length == 1) {
            $this->head = null;
            $this->tail = null;
        } else {
            $this->tail = $this->tail->prev;
            $this->tail->next = null;
            $temp->prev = null;
        }

        $this->length--;
    }

    public function remove($index)
    {
        if ($index < 0 || $index >= $this->length) {
            return null;
        }

        if ($index == 0) {
            return $this->popFirst();
        }

        if ($index == $this->length - 1) {
            return $this->popLast();
        }

        $temp = $this->getNode($index);

        $temp->next->prev = $temp->prev;
        $temp->prev->next = $temp->next;
        $temp->next = null;
        $temp->prev = null;

        $this->length--;
        return $temp;
    }
}

$dll = new DoublyLinkedList(2);

$dll->append(7);
$dll->append(3);
$dll->append(9);

// $node = $dll->getNode(1);
// echo $node->value; 

// $dll->setNode(1,54);

// $dll->prepend(15);

// $dll->insert(2, 77);

// $dll->popFirst();

// $dll->popLast();

// $dll->remove(2);

$dll->printAll();