#0223

Roman Numeral to Integer

MediumPython25 min20 XP

Problem

Convert a Roman numeral string to an integer. Handle subtractive cases like IV, IX, XL, and CM.

Why This Matters

Roman numeral parsing is a compact test of scanning rules and lookahead.

Function Signature

def roman_to_int(s):

Examples

Example 1

Inputs = "MCMXCIV"

Output1994

M = 1000, CM = 900, XC = 90, and IV = 4.

Constraints

Return the exact requested value.
Handle edge cases cleanly.
Prefer readable Python before micro-optimizing.

CodePython

def roman_to_int(s):
    """
    Input example: s = "MCMXCIV"
    Return: 1994
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return 0

def roman_to_int(s):
    """
    Input example: s = "MCMXCIV"
    Return: 1994
    Return the value from the function so the tests can compare it. Do not print unless the prompt asks.
    """
    # write your code here
    return 0

Visible browser tests run here when available.

Testcases1 visible / 3 hidden categories

Core example

Inputs = "MCMXCIV"

Expected1994

M = 1000, CM = 900, XC = 90, and IV = 4.

Hidden Test Categories

single symbolno subtractive pairsmultiple subtractive pairs