Relive PHP's quick sort

Rationale: Select any element in the current array (usually the first one) as the standard, create a new two empty array before and after the current array, and then iterate through the current array, if the element value in the array is less than or equal to the first element value, put it in an empty array, or put it behind an empty array.

1 / / quick sort
  2 function quick_sort($arr) {
  3 / / Get the number of array units
  4 $count = count($arr);
  5 / / determine the length of the array
  6 if ($count <= 1) {
  7 return $arr;
  8 } else {
  9 //Define two empty arrays
10 $before = $after = array();
11 // iterate over the array
12 for ($i=1; $i < $count; $i++) {
13 // judge by the first element
14 if ($arr[$i] <= $arr[0]) {
15 $before[] = $arr[$i];
16 } else {
17 $after[] = $arr[$i];
18 }
19 }
20 //Recursive call
21 $before = quick_sort($before);
22 $after = quick_sort($after);
23 //Merge array
24 return array_merge($before, array($arr[0]), $after);
25 }
26 }
27 //test
28 $arr = array(16, 9, 3, 12, 88, 19, 18, 16);
29 var_dump(quick_sort($arr));    

  

Relive PHP's quick sort