I applied through an ex-colleague's referral.

Had a call with the recruiter and hiring manager within the next week. Then I was ghosted for about 3 weeks. After sending multiple emails to the recruiter, she said she "missed" my application but that they would like to proceed with me to the next rounds.

Guess what? After that, I was ghosted for 3 more weeks. After multiple emails, they finally arranged the first interview, which was a coding interview. The interviewers asked 3 LC medium questions, all of which I answered correctly. Sure enough, I was being ghosted again after that.

At this point, I didn't really have any desire to work for the company, but I just wanted to see the end of it. So, I kept sending the recruiter emails asking about the status every week. Finally, after a couple of weeks, she replied that I was rejected and should have received an email from the system (hint: there was no such email in my inbox).

Worst interview experience ever.

Given a list of intervals, merge overlapping intervals.