Amazon OA, i.e. Amazon Online Assessment on platforms such as Hackerrank or Codility is the first step a candidate needs to take to get into an SDE role at Amazon. The assessment result will be used to decide if the candidate can move on to the phone or on-site (or virtual online aka VO) interviews.
This is a companion discussion topic for the original entry at https://algo.monster/problems/amazon_online_assessement_questions/