"as long as I neither named them nor posted the code to my solution"
rubbed me the wrong way. I get that certain things during the interview could be covered by NDA, but interview questions should not be one of them. There is no relationship between you and the company during the interview, there is no reason for them to hide their name or your solution.
I don’t have a strong opinion either way, but I’m sure that they don’t want the source posted such that a future interviewee would have access to it for their own solution.
"Unfortunately, I did not get the job. :)"
"as long as I neither named them nor posted the code to my solution"
rubbed me the wrong way. I get that certain things during the interview could be covered by NDA, but interview questions should not be one of them. There is no relationship between you and the company during the interview, there is no reason for them to hide their name or your solution.