Solutions for CodeWars @ https://www.codewars.com/
Codewars is a website with a vast number of user submitted code challenges. It has a low barrier to entry since all code is to be entered on the site and it's compiled and run on codewars servers.
Challenges are ranked and your user can rank up by solving the progressively more difficult challenges than your current rank.
I try to keep my solutions limited to 1 method call for easy copy paste into codewars IDE. Hence why you will see exessive use of local functions. Also keep in mind, these solutions are not to be considered "production grade" and is missing refactoring, various edge cases, exception handling amongst others. Solutions might also become out of date if challenge itself is changed. However, all solutions at submit time would have solved the current challenge.
Codewars is not the place to start if you are just learning programming. For people completely new to programming I recommend doing more typical "portfolio projects", since I believe you will get more experience from this which can be more closely translated to the typical programming role. When you have a good understanding of what good code/systemdesign is, you can attack these puzzles.
Codewars is a niche of programming more related to "competetive programming". In the real world there is a lot more to programming than these kinds of logic/math/programming puzzles. It is however a great way to challenge yourself since you can find puzzles on all levels. Also, it has become pretty popular for companies to ask these kinds of "puzzle like questions" during interviews.