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php实现映射操作实例详解

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本文实例讲述了php实现映射操作。分享给大家供大家参考,具体如下:

映射

映射,或者射影,在数学及相关的领域经常等同于函数。基于此,部分映射就相当于部分函数,而完全映射相当于完全函数.

映射(Map)是用于存取键值对的数据结构(key,value),一个键只能对应一个值且键不能重复.

实现

映射的实现方式可以使用链表或二叉树实现.

php实现映射操作实例详解

链表实现:

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<?php
/**
  * 接口 字典
  * Interface Dict
  * @package app\models
  */
Interface Dict
{
   public function set( $key , $value );
   public function get( $key );
   public function isExist( $key );
   public function delete ( $key );
   public function getSize();
}
class DictLinkList implements Dict
{
   protected $size =0;
   public $key ;
   public $value ;
   public $next ;
   public function __construct( $key =null, $value =null, $next =null)
   {
     $this ->key = $key ;
     $this ->value = $value ;
     $this ->next = $next ;
   }
   public function set( $key , $value ){
     $node = $this ;
     while ( $node && $node ->next ){
       if ( $node ->next->key== $key ){
         $node ->next->value = $value ;
         return $node ->next;
       }
       $node = $node ->next;
     }
     $node ->next = new self( $key , $value , $node ->next);
     $this ->size++;
     return $node ->next;
   }
   public function get( $key ){
     $node = $this ;
     while ( $node ){
       if ( $node ->key == $key ){
         return $node ->value;
       }
       $node = $node ->next;
     }
     throw new \Exception( 'cannot found key' );
   }
   public function isExist( $key )
   {
     $node = $this ;
     while ( $node ){
       if ( $node ->key == $key ){
         return true;
       }
       $node = $node ->next;
     }
     return false;
   }
   public function delete ( $key )
   {
     if ( $this ->size==0)
       throw new \Exception( 'key is not exist' );
     $node = $this ;
     while ( $node ->next){
       if ( $node ->next->key == $key ){
         $node ->next = $node ->next->next;
         $this ->size--;
         break ;
       }
       $node = $node ->next;
     }
     return $this ;
   }
   public function getSize()
   {
     return $this ->size;
   }
}

测试:

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<?php
     $dict = new DictLinkList();
     $dict ->set( 'sun' ,111); //O(n)
     $dict ->set( 'sun' ,222);
     $dict ->set( 'w' ,111);
     $dict ->set( 'k' ,111);
     var_dump( $dict ->get( 'w' ));  //O(n)
     var_dump( $dict ->isExist( 'v' ));  //O(n)
     var_dump( $dict -> delete ( 'sun' ));  //O(n)
     var_dump( $dict ->getSize());
/******************************************/
//111
//false
//true
//2

二叉树实现

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<?php
class DictBtree implements Dict
{
   public $key ;
   public $value ;
   public $left ;
   public $right ;
   private $size ;
   public function __construct( $key =null, $value =null)
   {
     $this ->key = $key ;
     $this ->value = $value ;
     $this ->left = null;
     $this ->right = null;
     $this ->size = 0;
   }
   public function set( $key , $value ){
     if ( $this ->size ==0 ){
       $node = new static ( $key , $value );
       $this ->key = $node ->key;
       $this ->value = $node ->value;
       $this ->size++;
     } else {
       $node = $this ;
       while ( $node ){
         if ( $node ->key == $key ){
           $node ->value = $value ;
           break ;
         }
         if ( $node ->key> $key ){
           if ( $node ->left==null){
             $node ->left = new static ( $key , $value );
             $this ->size++;
             break ;
           }
           $node = $node ->left;
         } else {
           if ( $node ->right==null){
             $node ->right = new static ( $key , $value );
             $this ->size++;
             break ;
           }
           $node = $node ->right;
         }
       }
     }
     return $this ;
   }
   public function get( $key ){
     if ( $this ->size ==0 )
       throw new \Exception( 'empty' );
     $node = $this ;
     while ( $node ) {
       if ( $node ->key == $key ) {
         return $node ->value;
       }
       if ( $node ->key > $key ) {
         $node = $node ->left;
       } else {
         $node = $node ->right;
       }
     }
     throw new \Exception( 'this key not exist' );
   }
   public function isExist( $key ){
     if ( $this ->size ==0 )
       return false;
     $node = $this ;
     while ( $node ) {
       if ( $node ->key == $key ) {
         return true;
       }
       if ( $node ->key > $key ) {
         $node = $node ->left;
       } else {
         $node = $node ->right;
       }
     }
     return false;
   }
   public function delete ( $key ){
     //找到元素,寻找元素左边最小元素
     $node = $this ->select( $key );
     if ( $node ->right!=null ){
       $node1 = $node ->selectMin( $node ->right);
       //替换当前node
       $node ->key = $node1 ->key;
       $node ->value = $node1 ->value;
       //删除$node->right最小元素,获取最终元素赋给$node->right
       $nodeMin = $this ->deleteMin( $node ->right);
       $node ->right = $nodeMin ;
     } else {
       $node1 = $node ->selectMax( $node ->left);
       $node ->key = $node1 ->key;
       $node ->value = $node1 ->value;
       $nodeMax = $this ->deleteMax( $node ->left);
       $node ->left = $nodeMax ;
     }
     return $this ;
   }
   protected function deleteMin( $node ){
//    if( $this->size ==0 )
//      throw new \Exception('empty');
//    $prev = new static();
//    $prev->left = $node;
//    while($prev->left->left!=null){
//
//      $prev = $prev->left;
//    }
//    $prev->left = $prev->left->right;
     if ( $node ->left==null ){
       $rightNode = $node ->right;
       $node ->right = null;
       $this ->size--;
       return $rightNode ;
     }
     $node ->left = $this ->deleteMin( $node ->left);
     return $node ;
   }
   protected function deleteMax( $node ){
     if ( $node ->right==null ){
       $leftNode = $node ->left;
       $node ->left = null;
       $this ->size--;
       return $leftNode ;
     }
     $node ->right = $this ->deleteMax( $node ->right);
     return $node ;
   }
   public function getSize(){
     return $this ->size;
   }
   public function select( $key ){
     $node = $this ;
     while ( $node ){
       if ( $node ->key== $key ){
         return $node ;
       }
       if ( $node ->key > $key ) {
         $node = $node ->left;
       } else {
         $node = $node ->right;
       }
     }
     throw new \Exception( 'this key not exist' );
   }
   public function selectMin( $node ){
     while ( $node ->left){
       $node = $node ->left;
     }
     return $node ;
   }
   public function selectMax( $node ){
     while ( $node ->right){
       $node = $node ->right;
     }
     return $node ;
   }
}

复杂度分析

链表 O(n) 。

二分搜索树 O(log n) 。

希望本文所述对大家PHP程序设计有所帮助.

原文链接:https://www.cnblogs.com/followyou/p/11388922.html 。

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