1st round by phone was called up by hr to fix a phone interview and then later I got a call, probably the manager or lead of a technology team I was asked non conventional questions where my approach to the question was studied rather than getting the solution. for example I was asked the complexity of binary search and even though I know the answer was logn I couldn't explain very clearly why it was logn verbally .

Great. Interviewers are nice. And basically behavioral questions. Once you got prepared for all it is not quite difficult to get the offer. But you need to be very familiar with your resume.