Thanks for the replies and help guys.
Looks like the ideas you gave are kinda beyond my actual knowledge.
The project is for Algorithm classes, so it doesn't check my programming knowledge. I perfectly understand how it should work, I can see that, and I can picture it in my head. But looks like the barrier is my knowledge about c++. I have no idea how I could possibly implement that in my program

I thought of reading the string 1 by 1, and when encountering a space (given the rule of writing in infix is to place spaces between numbers and operators), it would convert the already read string into an integer, and put it on a stack, and so on. But I have no idea how to implement that anymore :-/

I know, my fault I started so late with it, had health problems lately and other stuff to deal with meanwhile, I guess I wont pass that project class, heh.

Kind regards,
Adam.

P.s
Thanks for the welcome