如何在 PHP 中实现链表? PHP 中有内置的实现吗?
我需要做很多插入和删除操作,同时我需要保持顺序。
我想只使用 PHP,而不使用任何特殊扩展。
SplDoublyLinkedList
。这也可以吗?
这是一个 PHP 中的链表实现,取自:http://www.codediesel.com/php/linked-list-in-php/,它可以在 PHP 中添加、删除、反转和清空链表。
<?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;
$this->lastNode == NULL;
$this->count = 0;
}
//insertion at index
public function insert($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();
请注意,本文修复了一些错误。看评论。
这是在php中实现链表的代码,仅使用头节点即第一个节点的引用,然后在第一个、最后一个添加和删除一个键,并维护链表中键的代码。
<?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;
代码输出为:
$ php LinkList.php
199->100->LE->11->KP->45->FE->500->
Total elements 8
199->100->LE->11->KP->FE->500->
Total elements 7
199->100->LE->11->KP->FE->
Total elements 6
199->LE->11->KP->FE->
Total elements 5
这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;
输出为:
-0-2-3-4-5-7-10
-0-2-4-5-7-10
-2-4-5-7-10
我还尝试编写一个程序来用 PHP 创建链表。这是我写的,它对我有用。希望对回答问题有帮助。
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}
如果不认为大多数人都了解链表是什么。基本思想是您希望保持数据组织有序,以便您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、头部等,尽管是必要的,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 PHP 5.2.9 类。我想我必须自己实现它。
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 数组在底层是哈希表(不是简单的低级数组)。同时,您也无法获得指针的优势。 相反,您可以使用扩展来实现像链表这样的数据结构
forPHP,这意味着您正在实现一个数据结构inCtoPHP。 Spl数据结构是一个例子,另一个例子是php-ds扩展,特别是在链表的情况下,你可以使用这个:
https://www.php.net/manual/en/class.ds-sequence.phpSequence ADT 是 List ADT 和 Vector ADT 的统一,因此您可以使用 Sequence ADT 实现的数据结构作为列表。
希望这可以帮助人们做出明智的选择。