How to implement a fast sorting algorithm

Quick sort:

Code:

<?php/** Fast Sorting algorithm * 1. Find an element in the array as key, and generally take the first element of the array as key * 2. i=0, j= array Length-1 * 3. j--when Arr[j]<key, Arr[i] with arr[j] Swap position * 4. i++ when Arr[i]>key, Arr[i] with arr[j] Swap position * 5. 
Repeat 3,4 until i==j, complete. * 6. 
The left and right sets of elements separated by a key are then executed separately by 1,2,3,4,5 (recursion).  
      
* * $arr = array (); Create an array//This column more highlights: http://www.bianceng.cnhttp://www.bianceng.cn/Programming/sjjg/for ($i =0; $i <20; $i + +) {array  
_push ($arr, Mt_rand (1,200)); Echo ' source arr: '. Implode (', ', $arr). '  
      
<br> ';  
      
Quicksort ($arr, 0, Count ($arr)-1);  
      
Echo ' sorted arr: '. Implode (', ', $arr);  
    Quick Sort function quicksort (& $arr, $low, $high) {if ($low >= $high) {return;  
    } $i = $low;  
    $j = $high; $flag = 1;  
      
    0:I action 1:j Action $key = $arr [$low];  
                    while ($i < $j) {switch ($flag) {case 0://I if ($arr [$i]> $key) {  
                    $tmp = $arr [$i]; $arr [$i= $arr [$j];  
                    $arr [$j] = $tmp;  
                $flag = 1;  
                }else{$i + +;  
      
            } break;  
                    Case 1://J if ($arr [$j]< $key) {$tmp = $arr [$i];  
                    $arr [$i] = $arr [$j];  
                    $arr [$j] = $tmp;  
                $flag = 0;  
                }else{$j--;  
        } break;  
      
    }//Left arr quicksort ($arr, $low, $i-1);  
      
Right arr quicksort ($arr, $i +1, $high); }?>

Author: csdn blog proud Snow star Maple