My go-to for this sort of thing has always been Project Euler (https://projecteuler.net/).
I'd be more happy with a book that has 50 fairly simple apps to build in a simple language like Python where the apps aren't a whole lot longer than tic-tac-toe (~1/2 page).
The problems are mostly bioinformatics related, which often boils down to string manipulation/comparison, graph theory
https://github.com/seaneshbaugh/rosetta-euler
It's an ongoing thing I work on when I'm not working on anything in particular.
Dare you to add an HDL.
> I learned so much solving problem XXX so is it okay to publish my solution elsewhere?
It appears that you have answered your own question. There is nothing quite like that "Aha!" moment when you finally beat a problem which you have been working on for some time. It is often through the best of intentions in wishing to share our insights so that others can enjoy that moment too. Sadly, however, that will not be the case for your readers. Real learning is an active process and seeing how it is done is a long way from experiencing that epiphany of discovery. Please do not deny others what you have so richly valued yourself.
Just saying.
Although I agree with another poster that Euler is a bit math heavy, being able to submit a single number to check your solution is handy. Google's foobar recruiting puzzle system actually tests your program, but it's limited to Python and Java.