Hopper Software Engineer interview questions

First call with HR where you talk about yourself - pretty standard - a casual chat. I only made it to first round of technical interview. They had some pretty standard questions - what project are you proud of - explain me how you made the team grow and so on. They send you instructions on how to answer these questions before the interview. I guess if you do not follow that approach you have zero chance. You need to follow Situation - Task - Action - Result approach and talk numbers - which I did not. I guess it is a part of their requirement process - I am not sure as I can't know what exactly they did not like. Second half of the technical interview is a pretty standard question that you need to solve within 15-20 minutes. I was able to solve it but not in the way the person interviewing me expect me to solve I guess. He told me that I needed to use a Map.. I solved the question using a Set - I do not know if and why he did not like it despite code running and output being correct. I received the rejection email in 15 minutes.