Amazon Software Development Engineer interview questions

Very straightforward, but long. Have 4 back-to-back interviews, 45 minutes each. Each interview consisted of about 20 minutes of behavioral questions and a 25 minute technical question. There was a 30 minute break in the middle to go to the bathroom and get water.

The first question in the technical interview section was simple. As I solved it, they added more and more layers of complexity. I got it correct, but maybe my solution was suboptimal because I did not make it to the next intervie round.