Hey I got contact with a recruiter, then we talked about 30 minutes. One week after I had one phone interview. He asked me two coding questions and he also wanted me to prove mathematically why my solution is right. I did the coding problems and I prove what he wanted. After a week, they invite me for onsite interview. There were 4 interview. The first was more about my research and only one coding question. The last one was high level design question and the other two were just coding. I did pretty good, and I just made one silly mistake for implementing one problem. I figured it out after 10 min, but I had the feeling that the interviewer does not like it. That was the coding question at the end of the first interview. I think that killed me and I didn't get any offer.