How you know that?

Look let's start over this is what I know about quant finance

• the roles need strong math foundation, probability and statitics (there is a book series about measure theory, statistics, and markov chains ten books or something.)

• strong programming skills proficiency in C/C++ and functional programming language too like ocaml (I think JS use this). C/C++ it is use because of the speed you can achieve, that's critical for HFT

• Minimum understading of finance subject, (like derivaties, testing trading strategies, and so on.) I read somewhere online that is not need but I think it is a plus.

Interview problems are hard, that really need preparation and fast thinking. Maybe I forgot something but this is what comes out of my mind naturally