DigiCert Software Engineer interview questions

Applied through referral, Got shortlisted for an interview. Received an e-mail from DigiCert asking for interview availability. Round 1 was Scheduled Round 1:- DSA Round Usually in this round 2 questions are asked but I solved both with dry run and code in less than 20 minutes so was asked 3rd 😅, so I was pretty confident that I would clear this round 😬 In 2 days, i received an e-mail from DigiCert asking for round 2 availability. Round 2 was Scheduled. Round 2:- DSA + Design round The same day, HR calls at night to schedule HM round, was to schedule the next day that was Thursday but I had another 2 other interviews that day, so she asked for Friday but my luck I had committed 1 more interview that day, I asked for Monday but she told other candidates were in pipeline, so I asked to schedule my interview in evening on Friday. Round 3:- HM round, I was pretty sure I would clear this round, but that wasn't my day to say the least. Started off by asking intro, followed by standard questions why you want to switch, why digicert etc followed by project discussion and then same Merge Sort (which I implemented) without extra space complexity which I am still searching for if anyone finds it please do send me 😅 and finally a puzzle was asked which I solved. I had 50:50 feeling for this and that was friday night, trust me those 2 days till Monday when I can call the HR was one of the hardest times for me to spend ever (which by the way no one responded).