lol. I tried strcmp(card, &deck[i]) the whole time and did not get what I was doing wrong. Solid Solution. :)

Maybe try regular expressions, they are quite powerful but not that easy to get the actual pattern right

It's a 3 kyu, it's intended to be difficult.

The task might be easier than you think, and building a parser for arithmetic expressions is not that difficult. But not trivial either :)

I cannot crack this I think. My only idea on how to solve this would be creating an automata that reads the strings, but it seems like such an overkill. Is this the right way to go however?
Does anybody have a vague and non spoiler suggestion for another direction to go for cracking this problem?