通过不断的定位基准数的位置来实现快速排序

<?php  /**   * Created by PhpStorm.   * User: saint   * Date: 15/8/5   * Time: 上午11:49   */  class Demo  {      public $a = array(3, 6, 9, 2, 4, 7, 1, 5, 8, 0);         public function qsort($left, $right)      {          if($left > $right) {              return;          }             $i = $left;          $j = $right;          $standard = $this->a[$left];             while($i != $j) {                 // 从右向左查找比基准数小的单元              while(($standard <= $this->a[$j]) && ($j > $i)) {                  $j--;              }                 // 从左到右查找比基准数大的              while(($standard >= $this->a[$i]) && ($j > $i)) {                  $i++;              }                 $tmp = $this->a[$i];              $this->a[$i] = $this->a[$j];              $this->a[$j] = $tmp;          }             // 确定基准数的位置          $this->a[$left] = $this->a[$i];          $this->a[$i] = $standard;             $this->qsort($left, $i - 1);          $this->qsort($i + 1, $right);      }         // 执行函数      public function main()      {          $left = 0;          $right = count($this->a) - 1;          $this->qsort($left, $right);          print_r($this->a);      }  }     $demo = new Demo();  $demo->main();