# Make a calculator using Reverse Polish Notation. Use recursion.
# The Reverse Polish syntax completely removes the need for parentheses.
#
# Syntax examples:
# "3 + 2" -> ["3", "2", "+"]
# "3 * 4 + 2" -> ["3", "4", "*", "2", "+"]
# "3 * (4 + 2)" -> ["3", "4", "2", "+", "*"]
#
# Example for how to evaluate ["3", "4", "2", "+", "*"]:
# Start with "4 2 +" -> "6"
# Then "3 6 *" -> "18"
# Start with the "innermost" expression and work backwards (this is the recursion part)
#
# For help, email me@bchen.dev

# Use this function definition:
def rpn(expression: list[str]) -> int:
    return 0


# The following test cases should pass (please copy this into your code):
tests = [
    (["3", "2", "+"], 5),
    (["3", "4", "*"], 12),
    (["3", "4", "2", "+", "*"], 18),
    ([], 0),
    (["50", "2", "/"], 25),
    (["5", "2", "/"], 2),  # for division, cast to int using int(num)
    (["5", "4", "3", "-", "*"], 5),
]
for case in tests:
    result = rpn(case[0])
    expected = case[1]
    if result == expected:
        print(f"PASS: expected {expected}, got {result} for {case[0]}")
    else:
        print(f"FAIL: expected {expected}, got {result} for {case[0]}")