Another +1. These can be great ways to learn new languages. The later stages can be quite difficult but there’s so many years worth of challenges to mine from I

Another +1. These can be great ways to learn new languages. The later stages can be quite difficult but there’s so many years worth of challenges to mine from I can guarantee you won’t get bored even with the more basic problems. If you get stuck on a solution chances are someone else has already solved it in your language of choice which can also be great for learning.