OA:
Consisted of 7 debugging problems and MCQs. Time limit - 20 minutes.
2 coding problems. Time limit - 70 minutes.
Problem 1 : Related to comparator based sorting (Easy)
Problem 2 : Longest substring with exactly K distinct characters.
I passed all the test cases for both the problems and was called for Onsite Interviews after a week.
All the rounds were held virtually on Amazon Chime.
Virtual Technical Interview - Round 1: (45 minutes)
This was a pure DSA based round. The interviewer introduced himself and straightaway jumped into coding problems.
Problem 1 : https://leetcode.com/problems/nth-magical-number/ . Started with brute force and told approach using binary search.
Problem 2: Given an array. Find the minimum XOR among every possible pair of the array. Started with bruteforce, then sorting solution and at last Trie solution. Interviewer seemed happy.
Problem 3 : Given two integers A and B. Till the following condition isn't satisfied, keep substracting smaller number from the bigger number. Since, much time wasn't left, we just discussed about all possible approaches. Interviewer was trying to hint towards some log solution, but I couldn't catch it.
The following day I received a call from HR that I clear my 1st round and would proceed with the second round.
Virtual Technical Interview - Round 2: (45 minutes)
Problem 1 : Print the top view of the binary tree. Coded easily within 5-6 minutes after explaining.
Problem 2: https://leetcode.com/problems/lfu-cache/ . Unfortunately, here is where things started to go down hill. I didn't know the most optimal solution for this problem. Told all possible solutions I could think of. Spent around 20 minutes discussing and asked to write code. Wrote the not-so-optimal code. Interviewer wasn't much happy with the solution.
Some 10 minutes was left, hence interviewer asked some basic questions related to OS and DBMS. Answered them easily. And the interview ended.
2 days after the interview, I got the rejection mail. Though I felt very low and dissapointed because of this rejection, I am glad I made it this far. I can now work on my weak points.
My preparation : I have solved around 600 problems on leetcode. Amazon mainly focuses on clean production ready code. You must be able to come up with the most optimal solution.
I hope, this post helps someone in landing his/her dream job.
I will come back strong.
Good luck!