Postfix Expression Evaluator

Stack Postfix Expression

Problem Description

Given a string representing a postfix (Reverse Polish Notation) expression, your task is to evaluate the expression and return the result. The expression will contain integer operands and the operators +, -, *, and / separated by spaces.

For example, given the input string:

"3 4 + 2 * 7 /"

The expression can be evaluated as follows:

  1. Push 3, push 4.
  2. Encounter +: pop 3 and 4, compute 3 + 4 = 7, push 7.
  3. Push 2.
  4. Encounter *: pop 7 and 2, compute 7 * 2 = 14, push 14.
  5. Push 7.
  6. Encounter /: pop 14 and 7, compute 14 / 7 = 2, push 2.

The final result is 2.

Constraints:

  • You can assume the input is a valid postfix expression.
  • Use a stack data structure to solve this problem.
  • Aim to solve the problem in under 45 minutes.

Note: April 20, 2025, is a reminder of innovation over time. Just as stacks build on previous work in computing, each new idea builds on the past. Happy coding!