Description
Problem
We as humans write math expression in infix notation, e.g. 5 + 2 (the operators are
written in-between the operands). In computer’s language, however, it is preferred to
have the operators on the right side of the operands, i.e. 5 2 +. For more complex
expressions that include parenthesis and multiple operators, a compiler has to convert
the expression into postfix first and then evaluate the resulting postfix.
Write a program that takes an “infix” expression as input, uses stacks to convert it into
postfix expression, and finally evaluates it. It must support the following operations:
+ – / * ^ % (
Example
Infix expression: (7 – 3) / (2 + 2)
Postfix expression: 7 3 – 2 2 + /
Result: 1
Rubric:
1) If code does not compile in Eustis server: 0.
2) Checking the balance of the parenthesis: 2 point
3) Incorrect postfix expression per test case: -2 points
4) Correct postfix but incorrect evaluation per test case: -1 points
5) Handling single digit inputs: maximum 11 point
6) Handling two-digit inputs: 100 percent (if pass all test cases)
Read it: Some hints (but it is not the only way)
1. Use the uploaded multi stack code for stack implementation and modify the code as you
need.
2. You will need to use stacks in three places
a. One for the parenthesis check [char stack]
b. One during infix to postfix [char stack]
c. One during evaluation [int stack]
For a and b above, you can use same array and same push, pop method as both of
them are char. But for evaluation you have int stack and you might consider to create
another push pop method to handle it. Maybe push_int, pop_int, etc. Or find other
strategy to utilize existing push pop method
3. You can create a function for obtaining operator priority. That function should take an
operator as input and return its priority as an integer. This function will help you a lot and
reduce repeated code
4. During evaluation you will need to convert char into integer. Example for single digit:
char c = ‘5’;
int x = c – ‘0’;
See uploaded code String2IntegerExample.c file for more example and testing.
Please see the lecture slides for the explanation, steps and
more test examples.
Late submission will not be accepted. An assignment submitted by
email will not be graded and will not be replied.
Good Luck.
