How to setup a route for an optional second param?

Do I need to setup two rules in the Routes.php for these two urls?

Code:

1) http://mydomain.example/show-list
2) http://mydomain.example/show-list/25

PHP Code:

Rule 1) $routes->add('show-list', 'Home::index');
Rule 2) $routes->add('show-list/(:any)', 'Home::index'); 


Is there any way to achieve that in on rule? Just trying to avoid having to repeat it.

PHP Code:

//HomeController.php 
public function index()
{
 $user_id = $this->request->uri->getSegment(2);
 if($user_id != NULL) {
 //filter data by given user_id
 } else {
 //show all data
 }
 return view('listdata', compact('data');
} 


If I have only this rule

Code:

$routes->add('show-list', 'Home::index');

then it throws 404 file not found for url http://mydomain.example/show-list/25

If I have only this rule

Code:

$routes->add('show-list/(:any)', 'Home::index');

then it throws 404 file not found for url http://mydomain.example/show-list