Amazon Software Development Engineer interview questions

Recruiter scheduled the interview. - First round of interview. All high level development and design questions and description of experiences, challenges in job , and 1 online algorithmic coding session. All went well. -Selected for second round of interview. 1 online algorithmic coding session. Solved it recursively. Interviewer asked to do it iteratively. Solved it iteratively as well. Run time complexity was o(n). Have been asked to make it more efficient if possible. I was a bit confused. So, interview provider hints and I got what he was asking for. I explained him and he was satisfied. He, kind of provided hints positively to be ready for the next round. I assumed final onsite interview. So was preparing for it. :) After few days, Recruiter sent email that the team decided to go with another candidate. What the heck! Second round of interview was better than first round. Despite better performance, still not selected. Really Discouraging. Now don't even want to think of joining Amazon, I deserve Google. :)

Questions were asked from datastructures and os