NVIDIA Senior Software Engineer interview questions

3 telephonic discussion followed by 4 f2f interviews. I had a very bad experience, after going through 7 rounds of interview I did not get any feedback for HR, which I believe is very unethical. It was complete waste of time, except 1-2 interviewers they were all very sub standards. Hiring manger asked me about BST and he did not even know the time complexity of a search in BST. I really did not expect this low from Nvidia.

1 intro phone screening.... followed by hiring manager tech interview. then 4 interviews on a single day onsite.... final 2 rounds of onsite. Some algo related ques were asked... like fibonacci series. and quite a good amt of sql and few case studies- including data modelling. 1st and last round with the hiring manager. 1st round is technical and the last one mostly case studies on the related project they are planning u to hire