Adaptive Biotechnologies Software Engineer interview questions

First they gave me a take-home assignment. It had an algorithm problem, and OOP problem, a SQL problem, and a JavaScript problem. I moved on to the next round and talked to the recruiter which was non-technical and pretty simple, asking about availability and things like that. Then I had a technical phone screen. He asked to find which sets of 2 numbers in an array add up to 7. I solved it in n^2 complexity but he wanted it to be in n complexity. I couldn't figure it out so the interview ended earlier than expected and I wasn't invited to the virtual on-site.

You get hackerrank home assignment for 2 days. Inside, there is your very typical scholar do-you-know-your-trees assignment which has 4 sections and is pretty large. There are 4 junit tests and treenode java class for you. There is also a message that coding style and class reuse will be evaluated and it is equal in weight to passing all 4 tests. I knew already the assignments of this sort should be skipped since they rely on class design taste of reviewer. At this point I should have contacted recruiter and tell him I am to going to pass. However, I have never implemented Iterable interface so I decided to practice. Coding entire assignment took several hours. It is not professional on company's behalf to give so long assignments for pre-screen. Pre-screens so large are only seen in fintech industry. They are nowhere near fintech. After 4 test cases passed I submitted assignment; next morning got a reject from noreply@ address. No explanations, at all. I was not happy with code quality of original treenode class, by the way.