Got Falsely Accused of Cheating in a Job Interview

I was interviewing for a company, and in the design round, the interviewer first gave me a DSA question. I solved it pretty fast, and then he asked me to design a hotel booking system. I started by writing the entities, and out of nowhere, he asked, “Are you cheating?”

I was completely shocked and asked why he thought that. He said I was “looking sideways”—like, what?? Then he changed the question to an even easier one (flight booking), and I finished it in about 30 minutes. Right after that, he turned off his video and asked if I’ve any questions and ended the interview.

I still don’t understand what happened. Has anyone else experienced something like this?