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.