php实现映射操作实例详解

砸漏

发布于 2020-10-20 14:56:48

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发布于 2020-10-20 14:56:48

文章被收录于专栏：恩蓝脚本

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。

链表实现：

<?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：

<?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

<?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;
}
}