Written test requiring full working code; strong performance still no offer

Application

I applied through University. The process took 2 days. They shortlisted around 70 students based primarily on resume and projects. The first round was written test. We were given 3 algorithmic questions (fairly easy) and a database design question. We had to write the whole code and not just the pseudo-code. Around 15 people were shortlisted from this round based on written test and resume for the interviews. Even after acing the written test and having a fantastic resume, I wasnt selected.

Interview questions [1]

Question 1

Total number of set bits in all numbers till n.