Problem 1. Write a program to evaluate a postfix expression. Input: a postfix expression. E.g. 35+ Output: the result of the expression. E.g. the result for the above input is 8 Note: You must use the stack to implement this task. And please give the stack solutions for both the following implementations (a) Implement the array-based stack (b) Implement the pointer-based stack Test your program using the following expressions: 1. 35+ 2. 35 +6* 3. 356+ 4. 356 8-2-+ 5. 12 20 +16/