ACM is really demanding of mathematics. In ACM, many topics involve the knowledge of number theory, discrete mathematics, geometry, combinatorial mathematics and even calculus.

Of course, computational geometry is a big problem, so we can not discuss it in the field of mathematics for the time being, although the topic of computational geometry is basically required in every regional competition.

In my opinion, you should learn elementary knowledge of number theory, such as prime number, congruence, China remainder theorem, etc. These are all basic knowledge; After that, knowledge in discrete mathematics should also have concepts, such as classical logical relations and the concept of groups. Then learn the knowledge of combinatorial mathematics, especially permutation and combination, Polya theorem, pigeon coop principle and so on. These things, for each category, basically have corresponding topics to do on poj, and you can practice more on POJ. I have to say that ACM is a competition that needs a very solid programming foundation, and needs more practice and thinking!

The study of number theory must be reading books on elementary number theory, so I won't say this classic. . .

Combinatorial Mathematics can be seen in Lu Kaicheng's Combinatorial Mathematics or Wu's Combinatorial Mathematics in Programming.

I hope it works for you! I wish you good grades!

Your acm score in Huazhong University of Science and Technology is OK. When you have time, go to your ACM question bank to do questions and chat with your predecessors, which will greatly improve you!