public static function mergeSort($arr) { if (count($arr) == 1) { return $arr; } $left = $right = []; $middle = round(count($arr) / 2); for ($i = 0; $i < $middle; $i++) { $left[] = $arr[$i]; } for ($i = $middle; $i < count($arr); $i++) { $right[] = $arr[$i]; } $left = ITSP::mergeSort($left); $right = ITSP::mergeSort($right); return ITSP::mergeSortConquer($left, $right); }