Status : SDE at Product Based Company
Experience : 1 year
Education : Integrated Bachelors from Tier 1
Job Location : Bangalore

Round 1 (OA Hackerrank) : 2 SQL problems (medium level) , 5-6 MCQs from core Java concepts,
1 REST API based question - Given an author (A) and number of pages (N) as argument, Do an HTTP GET request to a (given) API (paginated) containing list of all books, filter out books by author A, fetch the data from the first N pages and return the list of titles as a list.
a) If the title is null, use story_title as the title.
b) if both title and story_title are null, ignore the value.

Round2 (DSA round) : 2 medium DSA problems:

1. https://leetcode.com/problems/set-matrix-zeroes/
2. https://leetcode.com/problems/minimum-size-subarray-sum/

Round 3 (DSA round): Backend concepts & 2 DSA problems (medium-hard)

Backend :

1. What is the use of @Transactional in Spring boot
2. Various ways to implement singleton pattern in Spring boot for repository class

DSA :

1. First non-repeating element in a stream of characters. Here the additional constraint was that the function returning the first non repeating character - getFnrc() should be O(1).
   Wasn't able to come up with a solution for O(1). The interviewer gave hints and finally the approach was to use doubly linked list/deque along with hashmap, similar to LRU cache.
2. https://leetcode.com/problems/remove-k-digits/
   Even though I had seen this question, I was nervous because of too much time wasted in the first problem, and was only able to solve it partially.
   However, the feedback was on the positive side, and I had one round remaining.

Round 4 (HM) : I was expecting a general discussion around projects and preparing around that. But the manager directly started with "Implement parking lot" and even though I was writing down some decent code, he interrupted because he didn't find any relevant OOPS concepts in my code.
Then he asked me few concepts around Java:

1. All OOPS concepts, which of them have you used in your project. Brief implementations of those codes.
2. Difference between List and ArrayList
3. Implementation of Singleton pattern in java, thread-safe
4. When and how to use Transactional and Rollback instances

Verdict : Rejected

Thoughts : Hiring manager round was the bomber. Got a bit nervous since I wasn't expecting LLD. Be prepared for everything .