/**
* Does not change object's loaded datastructure.
* Is a recursive function.
* @param DoubleLinkedList $list
* @return DoubleLinkedList
*/
public function mergeSort(DoubleLinkedList $list)
{
if ($list->count() < 2) {
return $list;
}
$array = $this->split($list);
$first = $this->mergeSort($array['firstPart']);
$second = $this->mergeSort($array['secondPart']);
return $this->merge($first, $second);
}
