A Reverse Polish Notation calculator. See more here: https://en.wikipedia.org/wiki/Reverse_Polish_notation.
The program is written as a solution to the LeetCode problem https://leetcode.com/problems/evaluate-reverse-polish-notation/.
The calculator supports integer operands, can do addition, subtraction, division and multiplication, and expects a valid input.
Example:
Input: tokens = ["2","1","+","3","*"]
Output: 9
Explanation: ((2 + 1) * 3) = 9