PHP链表

时间:2019-01-11
本文章向大家介绍PHP链表,主要包括PHP链表使用实例、应用技巧、基本知识点总结和需要注意事项,具有一定的参考价值,需要的朋友可以参考一下。
  /**
    * 链表 
    *     优点:可以不需要规定长度,任意添加或删除节点
    *     缺点:想要获取链表中的某个值,就需要遍历链表,直到找出这个值
    *     这个只是在演示,如果在并发环境中使用可能要加锁
    */
   
   class Node
   {
      private $value = null;

      private $next = null;

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

      public function setNext($node)
      {
         $this->next = $node;
      }

      public function getNext()
      {
         return $this->next;
      }

      public function getValue()
      {
         return $this->value;
      }
   }

   class Linked implements Countable, Iterator
   {
      private $head = null;

      private $tail = null;

      private $current = null;

      private $length = 0;

      /**
       * 添加节点
       * @AuthorHTL neetdai
       * @DateTime  2017-07-28T16:34:20+0800
       * @param     mixed     
       * 时间复杂度: O(1)              
       */
      public function add($value)
      {
         if ($this->head === null) {
            $this->head = new Node($value);
            $this->tail = $this->head;
            $this->current = $this->head;
         }else{
            $node = new Node($value);
            $this->tail->setNext($node);
            $this->tail = $node;
         }
         $this->length++;
      }

      /**
       * 删除指定位置的节点
       * @AuthorHTL neetdai
       * @DateTime  2017-07-28T16:38:21+0800
       * @param     int                   $position 位置
       * @return    bool   
       * 时间复杂度: O(n)                          
       */
      public function deletePosition($position)
      {
         if ($position > $this->length || $position <= 0) {
            return false;
         }

         $current = $this->head;

         $count = 1;

         //-------------------------------------
         //这一部分其实应该能写得更简单一些,可是我不懂得怎样写

         if ($position === 1) {
            $deleted = &$this->head;
            $this->head = $this->head->getNext();
            $this->length--;
            unset($deleted);
            return true;
         }

         $current = $this->head;
         for ($i=1; $i < $position - 1; $i++) { 
            $current = $current->getNext();
         }

         if ($current->getNext() === $this->tail) {
            $deleted = &$this->tail;
            $this->tail = $current;
            $this->tail->setNext(null);
            unset($deleted);
            $this->length--;
            return true;
         }

         $deleted = $current->getNext();
         $deleted = &$deleted;
         $current->setNext($deleted->getNext());
         unset($deleted);
         $this->length--;

         //-------------------------------------

         return true;
      }

      /**
       * 返回链表的长度
       * @AuthorHTL neetdai
       * @DateTime  2017-07-27T18:38:32+0800
       * @return    int
       * 时间复杂度: O(1)         
       */
      public function count()
      {
         return $this->length;
      }

      public function current()
      {
         return $this->current->getValue();
      }

      public function next()
      {
         $this->current = $this->current->getNext();
      }

      public function rewind()
      {
         $this->current = $this->head;
      }

      public function key()
      {
         return null;
      }

      public function valid()
      {
         return $this->current !== null;
      }
   }

   $l = new Linked();
   var_dump(count($l));
   $l->add(1);
   $l->add(2);
   $l->add(3);
   $l->add(4);
   var_dump(count($l));
   
   foreach ($l as $value) {
      var_dump($value);
   }
   
   $l->deletePosition(2);

   foreach ($l as $value) {
      var_dump($value);
   }

   $l->deletePosition(2);

   foreach ($l as $value) {
      var_dump($value);
   }

   $l->deletePosition(2);
   
   foreach ($l as $value) {
      var_dump($value);
   }

   $l->deletePosition(1);

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原文地址:http://www.manongjc.com/article/42699.html