I am currently a CS undergrad. my university offers no courses in Abstract algebra or Number theory or Topology or Analysis. recently I have got interested in Number theory in Discrete math course. moreover I was and still am interested in algebra too. but the problem is, can I apply to CS grad schools where I can research on Discrete math? of course I'll be working on Algebra (may Category theory or Group theory) or Number theory (whichever I prefer then) related problems in Discrete math there, if I am given opportunity to. again, what if my research is more mathematical than computational? I must mention here that, there is no community college or any uni or college which offer non degree courses in Abstract algebra, Number theory, Topology, Analysis, which would have fulfill my requirement for grad school in math, in my country.