用php实现链表

如何在PHP中实现链表？PHP中有内置的实现吗

我需要做大量的插入和删除操作，同时我需要保持顺序

---

我只想使用没有任何特殊扩展的PHP。这也可以吗？

这里是一个PHP中的链表实现，它可以添加、删除、反转和清空PHP中的linkedlist

<?php
class ListNode
{
    public $data;
    public $next;
    function __construct($data)
    {
        $this->data = $data;
        $this->next = NULL;
    }

    function readNode()
    {
        return $this->data;
    }
}

class LinkList
{
    private $firstNode;
    private $lastNode;
    private $count;

    function __construct()
    {
        $this->firstNode = NULL;
        $this->lastNode = NULL;
        $this->count = 0;
    }

    //insertion at the start of linklist
    public function insertFirst($data)
    {
        $link = new ListNode($data);
        $link->next = $this->firstNode;
        $this->firstNode = &$link;

        /* If this is the first node inserted in the list
           then set the lastNode pointer to it.
        */
        if($this->lastNode == NULL)
            $this->lastNode = &$link;
            $this->count++;
    }


    //displaying all nodes of linklist
    public function readList()
    {
        $listData = array();
        $current = $this->firstNode;
        while($current != NULL)
        {
            array_push($listData, $current->readNode());
            $current = $current->next;
        }
        foreach($listData as $v){
            echo $v." ";
        }
    }

    //reversing all nodes of linklist
    public function reverseList()
    {
        if($this->firstNode != NULL)
        {
            if($this->firstNode->next != NULL)
            {
                $current = $this->firstNode;
                $new = NULL;

                while ($current != NULL)
                {
                    $temp = $current->next;
                    $current->next = $new;
                    $new = $current;
                    $current = $temp;
                }
                $this->firstNode = $new;
            }
        }
    }



    //deleting a node from linklist $key is the value you want to delete
    public function deleteNode($key)
    {
        $current = $this->firstNode;
        $previous = $this->firstNode;

        while($current->data != $key)
        {
            if($current->next == NULL)
                return NULL;
            else
            {
                $previous = $current;
                $current = $current->next;
            }
        }

        if($current == $this->firstNode)
         {
              if($this->count == 1)
               {
                  $this->lastNode = $this->firstNode;
               }
               $this->firstNode = $this->firstNode->next;
        }
        else
        {
            if($this->lastNode == $current)
            {
                 $this->lastNode = $previous;
             }
            $previous->next = $current->next;
        }
        $this->count--;  
    }


       //empty linklist
    public function emptyList()
    {
        $this->firstNode == NULL;

    }


    //insertion at index

    public function insert($NewItem,$key){
        if($key == 0){
        $this->insertFirst($NewItem);
    }
    else{
        $link = new ListNode($NewItem);
        $current = $this->firstNode;
        $previous = $this->firstNode;

        for($i=0;$i<$key;$i++)
        {       
                $previous = $current;
                $current = $current->next;
        }

           $previous->next = $link;
           $link->next = $current; 
           $this->count++;
    }

    }   
}

$obj = new LinkList();
$obj->insertFirst($value);
$obj->insert($value,$key); // at any index
$obj->deleteNode($value);
$obj->readList();

---

以下是php中的代码，它将实现链表，只引用头节点即第一个节点，然后您首先添加、最后添加和删除一个键，并维护列表中键的代码

<?php

/**
 * Class Node
 */
class Node
{
    public $data;
    public $next;

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

/**
 * Class LinkList
 */
class LinkList
{
    public $head = null;

    private static $count = 0;

    /**
     * @return int
     */
    public function GetCount()
    {
        return self::$count;
    }

    /**
     * @param mixed $item
     */
    public function InsertAtFist($item) {
        if ($this->head == null) {
            $this->head = new Node($item);
        } else {
            $temp = new Node($item);

            $temp->next = $this->head;

            $this->head = $temp;
        }

        self::$count++;
    }

    /**
     * @param mixed $item
     */
    public function InsertAtLast($item) {
        if ($this->head == null) {
            $this->head = new Node($item);
        } else {
            /** @var Node $current */
            $current = $this->head;
            while ($current->next != null)
            {
                $current = $current->next;
            }

            $current->next = new Node($item);
        }

        self::$count++;
    }

    /**
     * Delete the node which value matched with provided key
     * @param $key
     */
    public function Delete($key)
    {
        /** @var Node $current */
        $current = $previous = $this->head;

        while($current->data != $key) {
            $previous = $current;
            $current = $current->next;
        }

        // For the first node
        if ($current == $previous) {
            $this->head = $current->next;
        }

        $previous->next = $current->next;

        self::$count--;
    }

    /**
     * Print the link list as string like 1->3-> ...
     */
    public function PrintAsList()
    {
        $items = [];
        /** @var Node $current */
        $current = $this->head;
        while($current != null) {
            array_push($items, $current->data);
            $current = $current->next;
        }

        $str = '';
        foreach($items as $item)
        {
            $str .= $item . '->';
        }

        echo $str;

        echo PHP_EOL;
    }
}

$ll = new LinkList();

$ll->InsertAtLast('KP');
$ll->InsertAtLast(45);
$ll->InsertAtFist(11);
$ll->InsertAtLast('FE');
$ll->InsertAtFist('LE');
$ll->InsertAtFist(100);
$ll->InsertAtFist(199);
$ll->InsertAtLast(500);

$ll->PrintAsList();
echo 'Total elements ' . $ll->GetCount();
echo PHP_EOL;
$ll->Delete(45);
$ll->PrintAsList();
echo 'Total elements ' . $ll->GetCount();
echo PHP_EOL;
$ll->Delete(500);
$ll->PrintAsList();
echo 'Total elements ' . $ll->GetCount();
echo PHP_EOL;
$ll->Delete(100);
$ll->PrintAsList();
echo 'Total elements ' . $ll->GetCount();
echo PHP_EOL;

我还试图编写一个程序，用PHP创建一个链表。这是我写的东西，它对我很有用。我希望这有助于回答这个问题

Created a php file. Name: LinkedList.php
{code}
<?php

require_once (__DIR__ . "/LinkedListNodeClass.php");

$node_1 = new Node();
Node::createNode($node_1, 5);
echo "\n Node 1 is created.";

$head = &$node_1;
echo "\n Head is intialized with Node 1.";

$node_2 = new Node();
Node::createNode($node_2, 1);
echo "\n Node 2 is created.";

Node::insertNodeInLinkedList($head, $node_2);

$node_3 = new Node();
Node::createNode($node_3, 11);
echo "\n Node 3 is created.";

Node::insertNodeInLinkedList($head, $node_3);

$node_4 = new Node();
Node::createNode($node_4, 51);
echo "\n Node 4 is created.";

Node::insertNodeInLinkedList($head, $node_4);

$node_5 = new Node();
Node::createNode($node_5, 78);
echo "\n Node 5 is created.";

Node::insertNodeInLinkedList($head, $node_5);

$node_6 = new Node();
Node::createNode($node_6, 34);
echo "\n Node 6 is created.";

Node::insertNodeInLinkedList($head, $node_6);

$node_7 = new Node();
Node::createNode($node_7, 99);
echo "\n Node 7 is created.";

Node::insertNodeInHeadOfLinkedList($head, $node_7);

$node_8 = new Node();
Node::createNode($node_8, 67);
echo "\n Node 8 is created.";

Node::insertNodeInHeadOfLinkedList($head, $node_8);

$node_9 = new Node();
Node::createNode($node_9, 101);
echo "\n Node 9 is created.";

Node::insertNodeAfterAPositionInLinkedList($head, 5, $node_9);

$node_10 = new Node();
Node::createNode($node_10, 25);
echo "\n Node 10 is created.";

Node::insertNodeAfterAPositionInLinkedList($head, 2, $node_10);

echo "\n Displaying the linked list: \n";
Node::displayLinkedList($head);

?>
{code}

This file is calling a class to create, insert and display nodes in linked list. Name: LinkedListNodeClass.php
{code}
<?php

class Node {
  private $data;
  private $next;

  public function __construct() {
    //does nothing...
  }

  //Creates a node
  public function createNode($obj, $value) {
    $obj->data = $value;
    $obj->next = NULL;
  }    

  //Inserts a created node in the end of a linked list
  public function insertNodeInLinkedList($head, &$newNode) {
    $node = $head;
    while($node->next != NULL){
      $node = $node->next;
    }
    $node->next = $newNode;
  }

  //Inserts a created node in the start of a linked list
  public function insertNodeInHeadOfLinkedList(&$head, &$newNode) {
    $top = $head;
    $newNode->next = $top;
    $head = $newNode;
  }

  //Inserts a created node after a position of a linked list
  public function insertNodeAfterAPositionInLinkedList($head, $position, &$newNode) {
    $node = $head;
    $counter = 1;
    while ($counter < $position){
      $node = $node->next;
      $counter++;
    }
    $newNode->next = $node->next;
    $node->next = $newNode;
  }

  //Displays the Linked List
  public function displayLinkedList($head) {
    $node = $head;
    print($node->data); echo "\t";
    while($node->next != NULL){
      $node = $node->next;
      print($node->data); echo "\t";
    }
  }
}

?>
{code}

创建了一个php文件。名称：LinkedList.php
{code}
{code}
此文件正在调用一个类来创建、插入和显示链接列表中的节点。名称：LinkedListNodeClass.php
{code}
{code}
这里是另一个使用元素数组的链表实现。add函数使元素保持排序

<?php

class LinkedList{

    private $_head = null;
    private $_list = array();

    public function addNode($val) {

        // add the first element
        if(empty($this->_list)) {
            $this->_head = $val;
            $this->_list[$val] = null;
            return;
        }

        $curr = $this->_head;

        while ($curr != null || $curr === 0) {

            // end of the list
            if($this->_list[$curr] == null) {
                $this->_list[$curr] = $val;
                $this->_list[$val] = null;
                return;
            }

            if($this->_list[$curr] < $val) {
                $curr = $this->_list[$curr];
                continue;
            }
            $this->_list[$val] = $this->_list[$curr];
            $this->_list[$curr] = $val;
            return;

        }

    }

    public function deleteNode($val) {

        if(empty($this->_list)) {
            return;
        }

        $curr = $this->_head;

        if($curr == $val) {

            $this->_head = $this->_list[$curr];
            unset($this->_list[$curr]);

            return;
        }

        while($curr != null || $curr === 0) {

            // end of the list
            if($this->_list[$curr] == null) {
                return;
            }

            if($this->_list[$curr] == $val) {
                $this->_list[$curr] = $this->_list[$val];
                unset($this->_list[$val]);
                return; 
            }

            $curr = $this->_list[$curr];
        }
    }

    function showList(){
        $curr = $this->_head;
        while ($curr != null || $curr === 0) {
            echo "-" . $curr;
            $curr = $this->_list[$curr];
        }


    }
}

$list = new LinkedList();

$list->addNode(0);
$list->addNode(3);
$list->addNode(7);
$list->addNode(5);
$list->addNode(2);
$list->addNode(4);
$list->addNode(10);

$list->showList();

echo PHP_EOL;
$list->deleteNode(3);

$list->showList();

echo PHP_EOL;

$list->deleteNode(0);

$list->showList();

echo PHP_EOL;

如果大多数人不理解链表是什么。其基本思想是，您希望保持数据的有序性，这样您就可以使用当前节点访问上一个和下一个节点。其他功能，如添加、删除、插入、头等，虽然是必要的，但都是糖。我认为SPL包确实涵盖了很多内容。问题是我需要一个PHP5.2.9类。我想我必须自己实现它。
只是澄清一下，在PHP中使用PHP数组实现链表可能不是一个好主意，因为PHP数组是隐藏的哈希表（不是简单的低级数组）。同时，指针也不会带来好处

相反，您可以使用扩展为PHP实现类似链表的数据结构，这意味着您在C到PHP中实现了一个数据结构

Spl数据结构就是一个例子，另一个例子是php ds extension，特别是在链表的情况下，您可以使用：

序列ADT是列表ADT和向量ADT的统一，因此可以使用序列ADT实现的数据结构作为列表

希望这能帮助人们做出明智的选择。
你能链接到一些简单的示例以快速入门吗？有什么。。。为什么PHP手册认为“数据结构”是一个单词“数据结构”？@BoltClock：你可以像往常一样为此提交错误报告；）你能进一步说明你最后想做什么吗？也许链表在这里不一定是正确的。PHP数组是有序的（与数组键无关）。也许这对你来说就足够了。它需要一个get函数，就像Java的List接口对LinkedList和ArrayList所具有的一样。
函数emptyList（）
不会重置
$this->count
。你能在线发布你的实现吗（github/gitlab/etc？），因为它不是答案，而是对其他答案的评论，所以被否决了
// Here's a basic implementation of SplDoublyLinkedList using PHP.
$splDoubleLinkedList = new SplDoublyLinkedList();
$splDoubleLinkedList->push('a');
$splDoubleLinkedList->push('3');
$splDoubleLinkedList->push('v');
$splDoubleLinkedList->push('1');
$splDoubleLinkedList->push('p');
// $splDoubleLinkedList->unshift('10');
// $splDoubleLinkedList->pop();
$splDoubleLinkedList->add(3, 3.0);
// First of all, we need to rewind list.
$splDoubleLinkedList->rewind();
// Use while, check if the list has valid node.
while($splDoubleLinkedList->valid()){
  // Print current node's value.
   echo $splDoubleLinkedList->current()."\n";
 // Turn the cursor to next node.
 $splDoubleLinkedList->next();
}

// Here's a basic implementation of SplDoublyLinkedList using PHP.
$splDoubleLinkedList = new SplDoublyLinkedList();
$splDoubleLinkedList->push('a');
$splDoubleLinkedList->push('3');
$splDoubleLinkedList->push('v');
$splDoubleLinkedList->push('1');
$splDoubleLinkedList->push('p');
// $splDoubleLinkedList->unshift('10');
// $splDoubleLinkedList->pop();
$splDoubleLinkedList->add(3, 3.0);
// First of all, we need to rewind list.
$splDoubleLinkedList->rewind();
// Use while, check if the list has valid node.
while($splDoubleLinkedList->valid()){
  // Print current node's value.
   echo $splDoubleLinkedList->current()."\n";
 // Turn the cursor to next node.
 $splDoubleLinkedList->next();
}