快速排序-php代码实现

<?php
function quicksort(array &$a)
{
    $n = count($a);
    quicksortinternally($a, 0, $n-1);
}
function quicksortinternally(array &$a, int $l, int $r)
{
    if ($l >= $r) return;
    $q = partition($a, $l, $r);
    quicksortinternally($a, $l, $q-1);
    quicksortinternally($a, $q+1, $r);
}
function partition(&$a, $l, $r): int
{
    $pivot = $a[$r];
    $i = $l;
    for ($j = $l; $j < $r; ++$j) {
        if ($a[$j] < $pivot) {
            $temp = $a[$i];
            $a[$i] = $a[$j];
            $a[$j] = $temp;
            ++$i;
        }
    }
    $temp = $a[$i];
    $a[$i] = $a[$r];
    $a[$r] = $temp;
    return $i;
}
$a1 = [1,4,6,2,3,5,4];
$a2 = [2, 2, 2, 2];
$a3 = [4, 3, 2, 1];
$a4 = [5, -1, 9, 3, 7, 8, 3, -2, 9];
quicksort($a1);
print_r($a1);
quicksort($a2);
print_r($a2);
quicksort($a3);
print_r($a3);
quicksort($a4);
print_r($a4);