Book recommendation : Olympiad Combinatorics book Can anyone recommend me an olympiad style combinatorics book which is suitable for a high schooler ? I know only some basics like Pigeon hole principle and stars and bars .
I hope to find a  book which contains problems which purely test our originality ( the problems with beautiful constructions like USAMO 2017 -TSTST P2: Which words can Ana pick?, Nim problems, games,tillings, etc ) . More specifically problems which doesn't require theory but requires out of the box thinking .
I don't know much about recurrence relations, generating functions or graph theory, so I would also love to see a book which introduces these topics .

I think Olympiad combinatorics book, by Pranav A. Sriram will help you much
https://artofproblemsolving.com/community/c6h601134
