Amazon Software Engineer interview questions

Got two technical phone interviews. All 45 minutes long but on separate days. The first interview asked about basic data structures and a question that is finding pairs in an array of integers, such that the two numbers in the pair sum to a fixed number. Then the second phone interview asked similar thing, but about tree. The first question is really easy, which is merging two sorted arrays into one array. The second question is to check if a binary tree is a binary search tree. Then I stopped at this step without going to onsite.

Initially I think there are a couple of phone interview rounds with a little tricky but simple questions on data structures and algorithms. It typically includes a programming task. They love the java collection framework, trees and graphs. Interviewers are nice to talk to and expect to understand your approach to a problem too.