PHP實現鏈表

目錄

• php實現對鏈表的增刪改查操做
• 利用鏈表實現棧
• 鏈表實現隊列

php實現對鏈表的增刪改查操做

定義節點類：

<?php
class Node
{
    public $val;
    public $next;



    public function __construct( $val = null, $next = null )
    {
        $this->val  = $val;
        $this->next = $next;
    }


}

鏈表類：

<?php
/**鏈表
 * Class Linklist
 * @package app\models
 */
class Linklist
{
    public $head;           //頭節點(默認一個虛擬頭節點)
    public $size;           //長度

    public function __construct()
    {
        $this->head = new Node();
        $this->size  = 0;
    }

    //頭插法
    public function addFirst( $value ){
//        $node = new Node($value);
//        $node->next = $this->head;
//        $this->head = $node;

        //簡化
//        $this->head = new Node( $value, $this->head );
//        $this->size++;

        $this->add(0,$value);
    }

    /**指定索引位置插入
     * @param $index
     * @param $value
     * @throws Exception
     */
    public function add( $index, $value ){

        if( $index > $this->size )
            throw new Exception('超過鏈表範圍');

//        if( $index==0 ){
//            $this->addFirst($value);
//        }else{
            $prev = $this->head;
            for($i=0;$i<$index;$i++){
                $prev = $prev->next;
            }

//            $node = new Node($value);
//            $node->next = $prev->next;
//            $prev->next = $node;

            $prev->next = new Node($value,$prev->next);
//        }

        $this->size++;
    }

    /**尾插法
     * @param $value
     */
    public function addLast( $value ){

        $this->add($this->size,$value);

    }


    /***
     * 編輯
     * @param $index
     * @param $value
     * @throws Exception
     */
    public function edit( $index, $value ){
        if( $index > $this->size-1 )
            throw new Exception('超過鏈表範圍');

        $prev = $this->head->next;
        for($i=0;$i<=$index;$i++){
            if( $i==$index )
                $prev->val = $value;
            $prev = $prev->next;
        }

    }

    /**
     * 查詢
     * @param $index
     * @return null
     * @throws Exception
     */
    public function select($index){
        if( $index > $this->size-1 )
            throw new Exception('超過鏈表範圍');

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


    /**刪除
     * @param $index
     * @throws Exceptionr
     */
    public function delete( $index ){
        if( $index > $this->size-1 )
            throw new Exception('超過鏈表範圍');

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

    /**檢索值是否存在
     * @param $value
     * @return bool
     */
    public function iscontain( $value ){
        $prev = $this->head->next;
        while( $prev ){

            if( $prev->val==$value ){
                return true;
            }
            $prev = $prev->next;
        }

        return false;
    }

    /**轉換爲字符串
     * @return string
     */
    public function tostring(){

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

        $r = [];
        while( $prev ){
            $r[] = $prev->val;
            $prev = $prev->next;
        }
        return implode('->',$r);

    }
    
     /**
      * 刪除指定的節點值
      * @param $value
      */
      public function removeFileds( $value ){
           $prev = $this->head;
           while( $prev->next ){
               if( $prev->val == $value ){
                   $prev->val = $prev->next->val;
                   $prev->next = $prev->next->next;
               }else{
                   $prev = $prev->next;
               }
           }
      }
      
       /**
        * 經過遞歸方式刪除指定的節點值
        * @param $value
        */
       public function removeFiledsByRecursion( $value ){
           $this->head = $this->removeByRecursion( $this->head ,$value);
           return $this->head;
       }
   
       public function removeByRecursion( $node , $value ){
               if( $node->next == null ){
                   return $node;
               }
               $node->next = $this->removeByRecursion( $node->next,$value );
           return $node->val == $value ? $node->next:$node;
       }   

}

調用操做以下：

<?php
$node = new Linklist();
$node->addFirst(1);
$node->add(1,7);
$node->add(2,10);
$node->edit(1,8);
var_dump($node->select(1)) ;
$node->delete(1);
$node->addLast(99);
var_dump($node->iscontain(2));
var_export($node);
var_export($node->tostring());

分析下鏈表操做的時間複雜度：

增： O(n)  只對鏈表頭操做：O(1)

刪： O(n)  只對鏈表頭操做：O(1)

改：O(n)

查：O(n)   只對鏈表頭操做：O(1)

利用鏈表實現棧

<?php
/**
 * 鏈表實現棧
 * Class LinklistStack
 * @package app\models
 */
class LinklistStack extends Linklist
{
    /**
     * @param $value
     */
    public function push( $value ){
        $this->addFirst($value);
    }

    /**
     * @return mixed
     */
    public function pop(){
        $r = $this->head->next->val;
        $this->delete(0);
        return $r;
    }
}

<?php
        $stack = new LinklistStack();
        $stack->push(1);
        $stack->push(3);
        $stack->push(6);
        $stack->push(9);

        print_r($stack->pop());
        print_r($stack->head);

鏈表實現隊列

<?php

/**
 * 鏈表實現隊列
 * Class LinkListQueue
 * @package app\models
 */
class LinkListQueue extends Linklist
{
    public $tail;    //尾節點

    /**
     * push
     * @param $value
     */
    public function push( $value ){

        if( $this->head->val==null ){
            $this->tail = new Node( $value );
            $this->head = $this->tail;
        }else{
            $this->tail->next =  new Node( $value );
            $this->tail = $this->tail->next;
        }
        $this->size++;
    }

    /**
     * pop
     * @return null
     * @throws \Exception
     */
    public function pop(){
        if( $this->size<=0 )
            throw new \Exception('超過鏈表範圍');
        $val = $this->head->val;
        $this->head = $this->head->next;

        $this->size--;
        return $val;
    }

    /**
     * 查看隊首
     */
    public function checkHead(){
        return $this->head->val;
    }

    /**
     * 查看隊尾
     */
    public function checkEnd(){
        return $this->tail->val;
    }

    /**
     * toString
     */
    public function toString(){
        $r = [];
        while( $this->head ){
            $r[] = $this->head->val;
            $this->head = $this->head->next;
        }
        return implode('->',$r);
    }
}

測試

<?php
$stack = new LinkListQueue();
        $stack->push(1);
        $stack->push(3);
        $stack->push(6);
        $stack->push(9);

        print_r($stack->pop());
        print_r($stack->head);
        print_r($stack->checkHead());
        print_r($stack->checkEnd());
        print_r($stack->toString());
/**        
1
app\models\Node Object
(
    [val] => 3
    [next] => app\models\Node Object
        (
            [val] => 6
            [next] => app\models\Node Object
                (
                    [val] => 9
                    [next] => 
                )

        )

)
3
9
3->6->9
**/