Tripadvisor Intern Software Engineer interview questions

Had interview at school's career service, first was provided with some class definitions( Coupon and Location where the locations have a parent location) and was asked to implement a method to find the best coupon according to a locationId. then we discussed its complexity. I felt not too bad but got the rejection letter. The feedback was didnt explain enough while i was writing the code.

This is actually the second round interview following up the on campus interview that I had about a month ago. It went quite well. The recruiter was a very nice guy and started the interview with some easy-going talking about my general experiences. Then I was asked two simple technical questions and I am not asked to write code but just talk about the algorithm. In the end I asked several questions and he told me there is going to be a onsite interview.