Amazon Software Development Engineer interview questions

I got an opportunity to interview for them in Hyderabad office from a friend. Through their employee referral process. It was a very long interview process, at least 4-5 interviews. I was given a 3 programming problems through interview street portal. They are not too hard, not too easy. one was to familirize myself with the platform, the other was given coordinates of two rectangles find out if they intersect and the last one was string search algorithm. all of them must pass all the test cases given.. after that I went thorough a telephonic interview. he too asked 3 questions. given an array of 2n+1 numbers in which every number except for one repeats twice.. you have to find out what that one number is.