IN C: My convertInToPost function is able to read white spaces, prioritize operators, balance parentheses, and read single digit numbers all using "if-else" statements. But I do not know how I will be able to have multi digit numbers be appended to postfix.

What condition should my "if statement" be within my convertInToPost function if I want it to read multi digit operands from an infix string?

If someone could help me with this, it would be most appreciated.

What I would like it to do: (all white spaces are intentional)

given infix: 2-(4*11+(6/7^8)*9)*200 postfix: 2 4 11 * 6 7 8 ^ /9 * + 200 * -