In geometry, you can look at Hunan white skin.
In the number theory part, Yu's writing is relatively safe.
Algebra. . . Read as much as possible and accumulate as much as possible. Pay attention to the way of deformation.
The final combination is not very good, because I learned it myself. If I want to recommend it, please read the first edition of the little blue book ... but how to say combination? The idea of cultivating combination is the most important. You can help me read some interesting math books. ...
This is just my humble opinion. I'm mediocre at saving the tournament myself. . .