I recently went through the interview loop for an L4 position at Google. The recruiter reached out to me at the end of March. I requested two weeks for preparation, and my phone screen was scheduled for mid-April.

Phone Screen: The question was similar to the "Text Justification" problem on LeetCode. There was a follow-up involving Binary Search. I coded the solution and explained my approach for the follow-up but couldn't complete the coding for it in time.

Verdict: Hire (the recruiter reached out to convey the verdict after two weeks). I asked for some additional time for the onsite rounds, which were scheduled for the end of May.

Round 1: I was asked about the longest consecutive subsequence. Follow-up 1: Find the longest increasing consecutive subsequence (elements must follow the input ordering). Follow-up 2: Find the longest increasing subsequence where adjacent elements can have a maximum difference of k. I coded solutions for the first two and explained my approach for the second follow-up.

Round 2: I was asked about reservoir sampling—given a comments link to a YouTube live stream, find a random user with uniform probability. Follow-up 1: Given a set of queries involving various times 't', return the most active user until that time. Follow-up 2: Return the top k most active users until time t. I coded the solution for the first follow-up and partially coded the solution for the second follow-up.

Round 3: I was given a binary matrix and asked to find the upper-left corner of the largest square of 1's. The follow-up question was: What if we are allowed to switch at most k zeros to 1's?

I emailed the recruiter several times but didn’t receive a response for two months. Today, the recruiter reached out and provided the following verdicts:

Round 1: Hire
Round 2: Leaning Hire
Round 3: Leaning Hire
Overall Verdict: Reject

The recruiter mentioned that there was nothing negative in my verdicts, but the hiring committee will reject my application for the L4 position.If they do, there will be 1 year cool down period. So, the recruiter suggested that I apply again after three months. I'm still not sure what went wrong.