I have two char string and they have '-' and '+' sign.
I want to pick a random sign from a variable. So far i tried like this, but it outputs only '+' - sign, how can i make it correct?
char plus = '+';
char minus = '-';
rand_symb = rand() % (plus - minus + 1) + minus;
You're choosing between two values, so you need to generate two random values. It's simplest to just generate 0 and 1:
int value = rand() % 2;
(Yes, rabid purists will tell you that this is doomed, because
rand() sucks, but it's good enough for what you're currently doing).
Based on that value, pick one of the two characters:
char ch = value ? '+' : '-';
or, to make the whole thing more compact:
char ch = rand() % 2 ? '+' : '-'.