Microsoft Software Development Engineer interview questions

I submitted my resume to a recruiter in a college career fair. 3 days later I received an email about on-campus interview. The on-campus interview took place after 2 weeks and consisted of a 1:1 interview with a technical manager from Windows Media Player Testing team. He was nice and everything. First half of the interview consisted of general questions about my projects and what I was working on. The second part was technical and he asked me a really simple question: Calculate factorial recursively. I coded on a piece of paper and spoke out loud the steps. And also wrote the special case checks and stuff. Then he asked the test cases and I gave the test cases(-ve numbers, characters,etc). Then he asked the complexity of the algorithm, where I stumbled a bit. But he helped me in that and we came up with the answer O(n). After that, I didn't hear from Microsoft in 3-4 weeks. I sent an email to the recruiter after 2 weeks without reply. On the 4th week, I was anxious, as I had an onsite interview with another company and emailed again. I got a reply that I was rejected :(