Samsung Electronics Software Developer interview questions

Interview have total 4 rounds : In first round , only one coding question was there having 3 hours time . In second round , interviewers asked DBMS ,OS , OOPS , DATA STRUCTURE, RAPID FIRE . In third round , bunch of coding questions. In fourth round : HR round

I visited Samsung in career fair. The recruiter asked about my interest in research or industry. Then he said they will contact me for scheduling an interview. They contacted me for scheduling the interview and said that it will have a 10 minutes for my presentation followed by questions. I replied them back and determined specific date and time for interview. They asked more questions about precise date and time and I answered to them, but they did not contacted for interview. I replied a few times for scheduling another time, but they did not reply at all. It was weird.