How to properly parse numbers in an arithmetic expression, differentiating positive and negative ones?

Question

I have an assignment in my Data Structures class in which I have to program a calculator that solves arithmetic expressions with the 4 basic operations and parenthesis, the inpu

Answer 1

That is the problem called "unary minus" and can in your case (no variables) get solved by substitution.

The operator - is an unary minus if it is

• preceded by a left parenthesis
• preceded by another operator
• the first character of the input

Now instead of storing a - you store a different character like, say m and assign it a higher precedence than the other operators (or the same as the exponentiation operator if you have one).

Another tip: don't use spaces to indicate anything, an arithmetic expression must work without any spaces or it is not correct.