RPN calculator

main.py

import math
from dataclasses import dataclass
from typing import Any, List, Optional  # noqa

import ipdb  # type: ignore


class Solution:
    functions = {
        "+": (lambda x, y: x + y),
        "-": (lambda x, y: x - y),
        "*": (lambda x, y: x * y),
        "/": (lambda x, y: math.ceil(x / y) if (x > 0 and y < 0) or (x < 0 and y > 0) else math.floor(x / y)),
    }

    def evalRPN(self, tokens: List[str]) -> int:
        stack: List[int] = [int(tokens[0])]
        for t in tokens[1:]:
            fn = self.functions.get(t, None)
            if fn is None:
                stack.append(int(t))
            else:
                v1 = stack.pop()
                v2 = stack.pop()
                stack.append(fn(v2, v1))
        return stack.pop()


@dataclass
class TestCase:
    input: list[str]
    expected_output: int


def main():
    testCases = [
        TestCase(input=["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"], expected_output=22),
        TestCase(input=["4", "13", "5", "/", "+"], expected_output=6),
        TestCase(input=["2", "1", "+", "3", "*"], expected_output=9),
        TestCase(input=["18"], expected_output=18),
    ]
    s = Solution()
    for tc in testCases:
        actual = s.evalRPN(tc.input)
        assert actual == tc.expected_output, f"\nExpected\n\t{tc.expected_output}\nGot\n\t{actual}\nFrom\n\t{tc.input}"

    print("All passed!")


"""
Constraints:

Ideas:

Test Cases:
["10","6","9","3","+","-11","*","/","*","17","+","5","+"]

stack = [17, 5]

cur = 17

"""