online-judge VS cms

For CS, you'll have a headstart if you have a bit of experience with Python and problem-solving. Search around for basic material on Python and if you have the time, attempt some problems on https://dmoj.ca/.

dmoj.ca ! It's meant more so for competitive coding but some of the problem sets they have fall under the Cryptography category.

If you want to host something yourself and don't mind doing the setup work, you can run your own instance of PC2 (which was formerly used by the ACM-ICPC contest) or DOMjudge or DMOJ.

The first type of practice is general problem solving. This is where you build up a strong intuition of problem and develop general problem solving techniques (but not memorising a huge list of techniques). Of course, the only way to improve is to do lots of problems / contests. For those who are more interested in competitive programming, I really like dmoj.ca (they host contests there as well, sometimes I author some :) ). The second type is just learning new concepts or techniques. I can't comment on courses such as "Grokking the Coding Interview" because I simply haven't done them. What I have enjoyed, however, is the CSES handbook (https://cses.fi/book/book.pdf). The book is very well written, and there is an additional problemset to test the concepts you just learnt at https://cses.fi/problemset/. Some of the concepts taught in the book are a bit out of scope for interviews, but would be great for anyone interested in competitive programming.

Personally, I’ve heard good stuff about DMOJ https://dmoj.ca/ Hope it helps :)

DMOJ

cms

If the latter, I would recommend looking into Contest Management System. It is written for programming competitions. Obviously you are not doing a programming competition and don't need a live scoreboard, etc., but there may be some elements of it you find useful.