Python: Convert a roman numeral to an integer

Last update on April 21 2025 12:55:08 (UTC/GMT +8 hours)

2. Convert a Roman Numeral to an Integer

Write a Python class to convert a Roman numeral to an integer.

Sample Solution:

Python Code:

class py_solution:
    def roman_to_int(self, s):
        rom_val = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
        int_val = 0
        for i in range(len(s)):
            if i > 0 and rom_val[s[i]] > rom_val[s[i - 1]]:
                int_val += rom_val[s[i]] - 2 * rom_val[s[i - 1]]
            else:
                int_val += rom_val[s[i]]
        return int_val

print(py_solution().roman_to_int('MMMCMLXXXVI'))
print(py_solution().roman_to_int('MMMM'))
print(py_solution().roman_to_int('C'))

Sample Output:

3986                                                                                                          
4000                                                                                                          
100

Pictorial Presentation:

Flowchart:

For more Practice: Solve these Related Problems:

• Write a Python class that maps Roman numeral characters to integer values and converts a Roman numeral string to an integer using a for-loop.
• Write a Python class that implements a reverse-lookup algorithm to handle subtractive notation in Roman numerals when converting to an integer.
• Write a Python class that validates Roman numeral input, ensuring it adheres to standard numeral rules before conversion.
• Write a Python class that provides both iterative and recursive methods for converting a Roman numeral to an integer and compares their performance.

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