Ask HN: Hiring Co doesn't want their algorithm problem solution shared? Comply?

A prospective employer had me solve a rather difficult(for me anyways) algorithm problem. In their instructions they say it should only take a couple hours and if you spend more than that just submit what you have. It ended up taking me more like 6-8 hours to find a solution. I think someone would be pretty much auto-rejected if they submitted a non complete solution. Anyways, I passed their first round and then they give me a 30 minute phone interview which consisted of a 10 minute code in a browser over the phone section which I did not pass and was given a rejection e-mail soon thereafter.

I then shared my solution to the algorithm problem on github. I'm still looking for a job on and off and it's my only project in c++. A couple months later someone from the company e-mails me saying other people have submitted my solution to their problem and asking me to take it down.

Should I comply? I feel like I don't owe them anything after I spent 10 hours for them and never even got to meet anyone face to face. I think they should create a new problem instead of re-using the same one. It's a lot of work on their end every time, but I don't think they really realize how many hours of prospective employees time they are wasting and I should be able to use it in my portfolio.