Introduction to Linked Lists in PHP: A Beginner&#s Guide

Links are a basic data structure in computer science. Its elements (called nodes) are connected in turn by pointer. Different from the array, the linked list is dynamic, which means that their size can grow or shrink without the need to adjust the size operation. This tutorial will introduce the basic knowledge of the linked list in PHP.

The structure of the linked list node

Each node in the linked list consists of two parts:

Data: The value stored in the node.

1. Next: Reference (pointer) to the next node.
The following is an example of implementing basic nodes in PHP:

Implement a simple linked list

<code class="language-php">class Node {
    public $data;
    public $next;

    public function __construct($data) {
        $this->data = $data;
        $this->next = null;
    }
}</code>

In order to manage the node, we create a LinkedList class that provides a method for the maintenance list and provides the method of operating it.

Basic operation

<.> 1. Add the node to the end

We add the node to the end of the list by reaching the iterative node until the last node reaches the last node.

<.> 2. Show the list

We can traverse the list to print all elements.

<code class="language-php">class LinkedList {
    private $head;

    public function __construct() {
        $this->head = null;
    }

    public function append($data) {
        $newNode = new Node($data);
        if ($this->head === null) {
            $this->head = $newNode;
        } else {
            $current = $this->head;
            while ($current->next !== null) {
                $current = $current->next;
            }
            $current->next = $newNode;
        }
    }
}</code>

<.> 3. Delete nodes

Delete nodes include finding nodes and updating the pointer of the previous node.

<code class="language-php">public function display() {
    $current = $this->head;
    while ($current !== null) {
        echo $current->data . " -> ";
        $current = $current->next;
    }
    echo "NULL\n";
}</code>

Example usage

The following is a method of implementing the linked list:

<code class="language-php">public function delete($data) {
    if ($this->head === null) {
        return;
    }

    if ($this->head->data === $data) {
        $this->head = $this->head->next;
        return;
    }

    $current = $this->head;
    while ($current->next !== null && $current->next->data !== $data) {
        $current = $current->next;
    }

    if ($current->next !== null) {
        $current->next = $current->next->next;
    }
}</code>

Output:

Conclusion

<code class="language-php">$linkedList = new LinkedList();
$linkedList->append(10);
$linkedList->append(20);
$linkedList->append(30);

echo "初始列表：\n";
$linkedList->display();

$linkedList->delete(20);
echo "删除 20 后：\n";
$linkedList->display();</code>

Links are powerful tools for dynamic data operation. Although PHP has built -in array functions, these functions usually have similar purposes, but understanding the linked list is essential for mastering the basic data structure and improving algorithm thinking. This is a starting point as a more advanced structure (such as a two -way linked list and a circular linked list).

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