function qsort(&$arr)
{
_quick_sort($arr, 0, count($arr) - 1);
}
/**
* 采用递归算法的快速排序。
*
* @param array $arr 要排序的数组
* @param int $low 最低的排序子段
* @param int $high 最高的排序字段
*/
function _quick_sort(&$arr, $low, $high)
{
$low_data = $arr[$low];
$prev_low = $low;
$prev_high = $high;
while ($low < $high)
{
while ($arr[$high] >= $low_data && $low < $high) {
$high--;
}
if ($low < $high) {
$arr[$low] = $arr[$high];
$low++;
}
while ($arr[$low] <= $low_data && $low < $high) {
$low++;
}
if ($low < $high) {
$arr[$high] = $arr[$low];
$high--;
}
}
$arr[$low] = $low_data;
if ($prev_low < $low) {
_quick_sort($arr, $prev_low, $low);
}
if ($low + 1 < $prev_high) {
_quick_sort($arr, $low + 1, $prev_high);
}
}
function quick_sort(&$arr)
{
$stack = array();
array_push($stack, 0);
array_push($stack, count($arr) -1);
while (!empty($stack)) {
$high = array_pop($stack);
$low = array_pop($stack);
$low_data = $arr[$low];
$prev_low = $low;
$prev_high = $high;
while ($low < $high)
{
while ($arr[$high] >= $low_data && $low < $high) {
$high--;
}
if ($low < $high) {
$arr[$low] = $arr[$high];
$low++;
}
while ($arr[$low] <= $low_data && $low < $high) {
$low++;
}
if ($low < $high) {
$arr[$high] = $arr[$low];
$high--;
}
}
$arr[$low] = $low_data;
if ($prev_low < $low) {
array_push($stack, $prev_low);
array_push($stack, $low);
}
if ($low + 1 < $prev_high) {
array_push($stack, $low + 1);
array_push($stack, $prev_high);
}
}
}
