The sample questions cover amortization, memory allocation, finite state machines, formal logic... If you just studied enough to pass a whiteboard interview, I'd hazard that you probably can't answer half of these questions without looking up what the symbols mean.

Sure, most people here may be able to figure out the PIN question, but it's not about whether any single question is easy or hard, but whether the test can sort the students according to ability. A good student may misread one or two, but a bad student is going to miss a lot more.