I checked the post (Where can I find programming puzzles and challenges?) where there's a lot of programming challenges and such, but after checking several of them, they all seem to be about algorithms and mathematics. Is there a similar site for purely logic/functionality-based challenges? For example:

- Retrieve data using a web service
- Generate output X from a CSV file
- Protect this code against SQL injection
- Make this code more secure
- What is wrong with this code (where the error is in logic, not syntax)
- Make this loop more efficient

Does a challenge site like that exist? Especially one that provides hints and/or correct solutions. That would be a very helpful learning site.