>>8427774Not necessarily. If the course is definition heavy, it will probably be quite effective. I would say a combination is often nice, since the flashcards would make you repeat the actual definitions, theorems and corollaries (etc), while problem solving and proofs let you work on the skills needed for those.
Sure, for a test, problem solving might be the best (as I said above, making flashcards a few days before a test is useless), but for becoming a good mathematician you have to know your definitions and theorems like the back of your hand. You do not learn these directly by solving problems (which is just learning and practicing algorithms and recognizing when to use which), you learn them by repeating them from time to time.