Detailed example of PHP's member ranking function based on doubly linked lists and sorting operations

<?php
/**
 * 双向链表实现用户排行榜
 *
 * 仅用于体现思想逻辑，不具备实际参考价值
 * @author 疯狂老司机
 * @date 2016-07-07
 */
class Rank{
  /**
   * @var 指向前一个节点的引用
   */
  public $pre = null;
  /**
   * @var 指向后一个节点的引用
   */
  public $next = null;
  /**
   * @var 用户排行id
   */
  public $id;
  /**
   * @var 用户名称
   */
  public $username;
  public function __construct($id = &#39;&#39;, $username = &#39;&#39;){
    $this->id = $id;
    $this->username = $username;
  }
  /**
   * 添加成员节点方法
   *
   * @access public
   * @param obj head 初始节点
   * @param obj rank 成员节点
   */
  public static function addRank($head, $rank){
    $cur = $head; // 辅助节点
    $isExist = false; //这是一个标志位
    while($cur->next != null){
      if($cur->next->id > $rank->id){
        break;
      }else if($cur->next->id == $rank->id){
        $isExist = true;
        echo&#39;<br/>不能添加相同的id&#39;;
      }
      $cur = $cur->next;
    }
    if(!$isExist){
      if($cur->next != null){
        $rank->next = $cur->next;
      }
      $rank->pre = $cur;
      if($cur->next != null){
        $cur->next->pre = $rank;
      }
      $cur->next = $rank;
    }
  }
  /**
   * 删除成员节点方法
   *
   * @access public
   * @param obj head 初始节点
   * @param obj rankid 用户排行id
   */
  public static function delRank($head, $rankid){
    $cur = $head->next;
    $isFind = flase; // 标记位
    while($cur != null){
      if($cur->id == $rankid){
        $isFind = true;
        break;
      }
      $cur = $cur->next;
    }
    if($isFind){
      if($cur->next != null){
        $cur->next->pre = $cur->pre;
      }
      $cur->pre->next = $cur->next;
      echo &#39;<br/>要删除的成员id是&#39;.$cur->id;
    }else{
      echo&#39;<br/>要删除的成员没有&#39;;
    }
  }
  /**
   * 遍历所有节点并输出显示
   *
   * @access public
   * @param obj head 初始节点
   */
  public static function showRank($head){
    $cur = $head->next; // 不打印空节点
    while($cur->next != null){
      echo&#39;<br/>id=&#39;.$cur->id.&#39; &#39;.&#39;username=&#39;.$cur->username;
      $cur = $cur->next;
    }
    echo&#39;<br/>id=&#39;.$cur->id.&#39; &#39;.&#39;username=&#39;.$cur->username;
  }
}
//创建一个初始节点
$head=new Rank();
//创建一个成员
$rank=new Rank(1,&#39;老王&#39;);
Rank::addRank($head,$rank);
$rank=new Rank(2,&#39;小明&#39;);
Rank::addRank($head,$rank);
$rank=new Rank(6,&#39;大熊&#39;);
Rank::addRank($head,$rank);
$rank=new Rank(3,&#39;静香&#39;);
Rank::addRank($head,$rank);
$rank=new Rank(56,&#39;孙二娘&#39;);
Rank::addRank($head,$rank);
echo &#39;<br/>成员排行榜.....&#39;;
Rank::showRank($head);
echo&#39;<br/>&#39;;
echo &#39;<br/>删除后的成员排行榜.....&#39;;
Rank::delRank($head,3);
Rank::showRank($head);
echo&#39;<br/>&#39;;
echo&#39;<br/>下面测试删除最前面的和最后面的成员<br/>&#39;;
echo &#39;<br/>删除后的成员排行榜.....&#39;;
Rank::delRank($head,1);
Rank::showRank($head);
echo&#39;<br/>&#39;;
echo &#39;<br/>删除后的成员排行榜.....&#39;;
Rank::delRank($head,56);
Rank::showRank($head);
?>