php实现归并排序

function mergeSort($arr) {
$length = count($arr);

if ($length <= 1) {
    return $arr;
}

$mid = (int)($length / 2);
$left = array_slice($arr, 0, $mid);
$right = array_slice($arr, $mid);

$left = mergeSort($left);
$right = mergeSort($right);

return merge($left, $right);

}

function merge($left, $right) {
$result = [];
$leftLength = count($left);
$rightLength = count($right);
$i = $j = 0;

while ($i < $leftLength && $j < $rightLength) {
    if ($left[$i] <= $right[$j]) {
        $result[] = $left[$i];
        $i++;
    } else {
        $result[] = $right[$j];
        $j++;
    }
}

while ($i < $leftLength) {
    $result[] = $left[$i];
    $i++;
}

while ($j < $rightLength) {
    $result[] = $right[$j];
    $j++;
}

return $result;

}

// 示例使用
$numbers = [5, 2, 8, 12, 3];

$sortedNumbers = mergeSort($numbers);

print_r($sortedNumbers);