It was easy question and I provided brute force and optimized way. Before I could start coding, I was told to pick any of the approached to code. So I picked faster to code which was brute force way, which interviewers were ok as well. When I found a bug in the code and tried to fix, i was stopped doing it. I guess bugs are not expected in the code or maybe a super human kind of software engineers are needed. Response to my follow up questions were not clear, especially related to the role. Later when I asked what are the challenges for an EM, i was told that i was being interviewed for backend engineer role. Pretty bad experience. :( Sorry Shippo, try to be consistent and transparent upfront.