There were 2 different rounds. The first round a question about merging lists with some given api was asked. Implemented the working solution correctly with given time complexity. In the 2nd round, another question about some array was asked which I later figured out was some standard geeksforgeeks trick question. Implemented the solution with required time complexity. Asked the interviewer if he wants to ask any more questions and he said no. After the 2nd round, I was said they don't want to go forward without giving any proper explanation. This is really unprofessional and in-ethical. Don't get me wrong, I've been rejected by interviews before, but in every one of them there were valid reasons, like I didn't solve this question correctly and this should be the correct solution or they couldn't apply for the visa currently, but rejecting a candidate when he solved both questions correctly and without any proper explanations is highly unprofessional .
tl;dr: Don't waste your time giving interviews for a unprofessional company. I should've come here before and read the other reviews before wasting my time. You'll not learn anything new from the interviews and they'll just reject you whimsically.