Seeing the other solutions, definitely not a clever solution nor a best practice ^_^

• The RegExp could be shorter
• Instead of using RegExp, substring would've been even easier
• The matches are nullable, which make it difficult to convert to int
  Thanks for sharing everyone :)

The use of singleWhere is brilliant! Why write new logic when the language already provides it :)

I like how clean the code is, but from a optimization point of view I don't think it's very efficient to always iterate the entire List. Or am I missing something?

I really like this solution, clever approach! Didn't look at the puzzle this way :)

Wow, I'm really surprised by the creativity in this solution! :) Did you go for solution with that in mind?

Well, for me it actually is.. I have a hard time grasping the overall idea behind this solution. Requires some studying to figure this out.

Really like this solution. Though it might seem overkill, I think this extreme OOP approach makes this piece of code really transferable to other developers of different skill levels. I can see your thought process just by scanning the classes and methods :-)

A positive shock?

Love how clean and readable this is :)

@JebPotly you weren't the only one, I too was a bit confused. I consider it to be a part of the exercise though, figuring out what the task on hand actually is.

Anyway, @donaldsebleung: loved the kata! Thanks for providing it :-)

Thanks :-)