快速排序

 1 $arr=array(33,2,54,25,65,34,67,42,87,90,243,213,365,78,67,345,678);
 2 
 3 function quick_sort($arr){ 
 4     $len = count($arr); 
 5     if($len <= 1) 
 6     { 
 7         return $arr; 
 8     } 
 9     $key = $arr[0]; 
10     $arr_left = array(); 
11     $arr_right = array(); 
12     for ($i=1;$i<$len;$i++) 
13     { 
14         if($arr[$i] <= $key){ 
15             $arr_left[] = $arr[$i]; 
16         }else{ 
17             $arr_right[] = $arr[$i]; 
18         } 
19     } 
20     $arr_left = quick_sort($arr_left); 
21     $arr_right = quick_sort($arr_right); 
22     return array_merge($arr_left,array($key),$arr_right); 
23 }
24 
25 echo '<pre>';
26 print_r(quick_sort($arr));
27 echo '</pre>';