Divisibility

Combinatorics

Bitwise operations

https://youkn0wwho.academy/topic-list

Use this.This has all the math topic that you'll ever require in cp. Just start with some common topics.There are quite high lvl topics also just skip them for now

Yeah I was shocked too I think cpalgorithms number theory section is great

I'm certainly not an expert but I am definitely better at math than coding for now. I don't think you needed a deep mathematical understanding to solve todays problems. For problem b for example, you just go, when does a light get changed? It has a divisor. For every divisor it as another number than goes with it right? (like 2 and 3 make 6). Does this mean every light stays on? Nah, when is the number of (unique) divisors not even. A perfect square. If you don't believe that a number has an odd num of divisors iff it is a perfect square. Try proving that an even number of divisors implies a number is not a perfect square, this is an equivalent statement in fact. After that the problem breaks down.

I'm by no means a great coder, in fact, I had a horrible contest because I didn't know the sqrt function was imprecise, which wasted me like 40 mins, but I hope what I said makes sense. Cheers!