you got several errors in your code .

1- in int faq_choice,faq_YN;
y did u make faq_YN integer it have to be char that is why the infinite loop occurs.

2- in your if statements u made && it...

You can traverse through the string using a pointer ofcourse :-
-if u find any open braces (and i mean OPEN ' (,{,[ ') Push it to the stack.
-While u still traversing the expression if u find...