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我正在尝试使用 PHP 实现一个链表。我已经完成了其中的一部分，但是，我不确定我的代码是否正确。您能否建议如何在指定索引处添加/删除特定节点？

请参考以下代码：（共3个文件）

1) [ListNode.class.php]

我定义的节点结构：

<?php


class ListNode
{
    protected $next;        // Next node in the list
    protected $value;       // Value of the node

    // Constructor
    // Input: Value of the node
    public function __construct($value)
    {
        $this->value = $value;
        $this->next = NULL;
    }

    public function __get($name)
    {
        return $this->$name;
    }

    public function __set($name, $value)
    {
        $this->$name = $value;
    }

    // Return the node as string
    public function toString()
    {
        return $this->value . "\n";
    }
}

2) [LinkList.class.php]

链表和我没有完成的操作：

<?php


require('ListNode.class.php');

class LinkedList
{
    protected $first;           // First node of the list
    protected $last;            // Last node of the list
    protected $count;             // Total numbers of nodes in the list

    // Constructor
    // Input: Array of values (Optional)
    public function __construct($values = array())
    {
        $this->first = null;
        $this->last = null;
        $this->count = 0;

        foreach ($values as $value) {
            $this->add($value);
        }
    }
    public function isEmpty()

        if ($this->sizeOf() !== 0) 
        return ($this->first == NULL);
    }

    // Add a node at the beginning of the list
    public function add($value)
    {
        $link = new ListNode($value);
        $link->next = $this->first;
        $this->first = &$link;

        if($this->last == NULL)
           $this->last = &$link;

        $this->count++;
    }

    // Add a node at the specified index
    public function addAtIndex($value, $index)
    {

    }

    // Remove a node at the end of the list
    public function remove()
    {
        if($this->first != NULL)
        {
          if($this->first->next == NULL)
          {
            $this->first == NULL;         
            $this->cout--;
        }
        else
        {
             $previous = $this->first;
             $current = $this->first->next;

             while($current->next != NULL)
             {
              $previous = $current;
              $current = $current->next;

             $previous->next = NULL;
             $this->count--;
        }
    }

    // Remove a node at the specified index
    public function removeAtIndex($index)
    {

    }

    // Return the value of the first node
    public function getNode()
    {

    }

    // Return the value of the node at the specified index
    public function getNodeAtIndex($index)
    {
         if($index <= $this->count)
        {
            $current = $this->firstNode;
            $pos = 1;
            while($pos != $index)
            {
                if($current->next == NULL)
                    return null;
                else
                    $current = $current->next;

                $pos++;
            }
            return $current->value;
        }
        else
            return NULL;  
    }

    // Return the number of nodes
    public function sizeOf()
    {
        return $this->count;
    }

    // Return the list as string
    public function toString()
    {
        $list = "";
        $node = $this->first;

        while ($node != null) {
            $list .= $node->toString();
            $node = $node->next;
        }

        return $list;
    }
}
4

1 回答 1

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如果您需要一个链表，为什么不使用标准 PHP 库呢？您拥有SplDoublyLinkedList所需的所有功能：

这些方法是实现ArrayAccess接口的一部分，这意味着您不必直接调用它们，但可以执行以下操作：

$list = new SplDoublyLinkedList;
$list->push('item 1');
$list->push('item 2');
$list->push('item 3');
echo $list[1];
unset($list[1]);

foreach($list as $index => $value) {
    echo "\n$index: $value";
}

输出：

item 2
0: item 1
1: item 3
于 2013-02-23T16:43:57.847 回答