The first interview was mainly focused on C++ programming ability. You are expected to come up with a solution to a completely new problem. The problems were hand-crafted by the interviewer, so don't expect anything from Leetcode to help you out haha. The second interview is mainly about hardware and HDL programming ability. Make sure to understand Computer System Architecture fundamentals and do more practice for Verilog or some other HDL of your choosing. Again, the problems will NOT be conventional in any sense.