I had a working solution but their feedback was it didn't demonstrate my iOS skills because rather than using the standard TableView/CollectionView I used a library. The problem beforehand did not mention that not using libraries was a requirement. Their direct feedback was that the code was very clean and worked well but since they couldn't determine my skills because I used a library they turned me down. I felt their recruiter and interview process was disrespectful of my time - particularly since the recruiter mentioned the coding problem beforehand was optional.