The very first phone call starts with a recruiter. They ask me some basic questions, e.g., graduate date and skill sets. Plus, there's a very easy question about finding the singleton number from an array.

Second phone call is about my resume and an easy problem to find anagrams in a dictionary from text.

Third phone call is about finding the median, average, or mode from an infinite stream of numbers. Still pretty easy, and I finished within 35 minutes. This time, the interview was conducted with an online editor.

Onsite: The hotel is pretty fancy.

The first interview was about designing a mini-Yelp, pretty standard design questions, and how to test this mini-Yelp.

The second interview was really, really disappointing. The interviewer came into the room in a kind of shabby t-shirt. They were still sleepy and seemed like they had just gotten out of bed a minute ago. They spent some time thinking about what question to give. Finally, they came up with a DAG question, which was about how to detect a potential cycle in a DAG. I solved it with DFS in a short time. But then the interviewer began asking vague questions. They said my solution could return "false true" and asked me to provide those cases. I thought there was a bug in my code, but after checking it again and again, my solution was clean. The interviewer still insisted on that, and I got confused. The interviewer should have provided the case to show that my solution would return "false true" instead of me. The interviewer was pretty impatient and kept fidgeting in their chair, playing with their toes (seriously, playing with their toes). After a while of discussing, I tried all possible solutions I could think of. They stood up and made a case on the whiteboard. I think it was 5 minutes before the end that I finally understood their intention. There were no mysterious algorithms or magical solutions, just a little trick to create confusion. Communication with that interviewer was really bad, and I believe their words misled me down a wrong path to understanding the question. That made me want to leave their office immediately.

The third interviewer was totally different. This interviewer was polite and patient. We started talking about projects I had been through and some easy problems. We progressed step-by-step to harder and harder problems, and I solved each of them on the whiteboard with clean code (I believe it is clean). I even believe one could just copy and paste that code into a computer and run it with no problems. The interviewer was pretty satisfied and wished we could have had more time for discussion.

The question I want to ask is, how could these two different interviewers exist on the same team?

Average questions. No complex or complicated solutions.