Disappointed in Myself After My Meta Interview

I've been preparing on and off for over a year, constantly trying to get calls from leading companies. Finally, I received an interview invitation from Meta for a Software Engineer role, which felt like a significant breakthrough as it was the first FAANG company to reach out to me after numerous applications. I asked for three weeks to prepare and dedicated that time to solving around 150 Meta-tagged problems.

On the interview day, I faced two coding challenges. The first was 'Missing Elements in Sorted Array'. I managed to solve it, although I felt I struggled a bit with explaining my thought process. The second question was 'All Nodes Distance K in Binary Tree'. I was genuinely happy to see this problem as I was quite familiar with it. I almost made a mistake but caught it during my dry run and corrected it. I left the interview feeling confident that I had performed well and would advance to the next round.

However, a few hours later, a crushing realization hit me: I had completely forgotten to implement a visited set in my BFS approach for the second problem. This oversight rendered my entire solution incorrect. The very next day, I received a rejection email. A small part of me had hoped for a different outcome, but it wasn't meant to be. This experience has left me feeling quite disheartened, especially after dedicating three weeks to intense preparation that now feels wasted. I also acknowledge my weaknesses in LLD/HLD, which have been factors in previous interview failures, and this latest rejection just adds to a streak of disappointments.