Sai A Sai A
Updated date Jan 13, 2024
In this blog, we will learn multiple methods to convert Roman numerals to Arabic numerals, from a simple approach to complex recursive solutions and an object-oriented manner.

Introduction:

Roman numerals are old numbers that people used for a long time. Even though they might seem complicated, we are going to learn how to change them into regular numbers using a computer language called Python. This blog post will show you different ways to do it. By the end, you'll be able to understand and use Roman numerals easily.

Method 1: The Straightforward Approach

Let's start with a simple and direct method to convert Roman numerals to Arabic numerals. We'll use a dictionary to map each Roman numeral symbol to its corresponding value. The program will iterate through the input string, adding the values together according to the rules of Roman numerals.

def roman_to_arabic(roman):
    roman_numerals = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
    result = 0

    for i in range(len(roman)):
        current_value = roman_numerals[roman[i]]
        if i + 1 < len(roman) and roman_numerals[roman[i + 1]] > current_value:
            result -= current_value
        else:
            result += current_value

    return result

# Example Usage
input_roman = "XIV"
output_arabic = roman_to_arabic(input_roman)
print(f"{input_roman} in Arabic numerals: {output_arabic}")

Output:

XIV in Arabic numerals: 14

The program iterates through each character of the Roman numeral string, adding or subtracting values based on the rule that smaller numerals preceding larger ones are subtracted.

Method 2: Recursive Exploration

Now, let's explore a recursive approach to the Roman numeral conversion. This method breaks down the problem into smaller sub-problems, making the code more elegant.

def roman_to_arabic_recursive(roman):
    roman_numerals = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}

    if not roman:
        return 0

    current_value = roman_numerals[roman[0]]
    if len(roman) > 1 and roman_numerals[roman[1]] > current_value:
        return -current_value + roman_to_arabic_recursive(roman[1:])
    else:
        return current_value + roman_to_arabic_recursive(roman[1:])

# Example Usage
input_roman_recursive = "XIV"
output_arabic_recursive = roman_to_arabic_recursive(input_roman_recursive)
print(f"{input_roman_recursive} in Arabic numerals: {output_arabic_recursive}")

Output:

XIV in Arabic numerals: 14

This recursive approach elegantly handles the conversion by breaking the problem down into smaller sub-problems, providing a clear and concise solution.

Method 3: Object-Oriented Approach

For a different perspective, let's create a RomanNumeral class that encapsulates the conversion logic. This approach allows for better organization and reusability.

class RomanNumeral:
    def __init__(self, roman):
        self.roman_numerals = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
        self.roman = roman

    def to_arabic(self):
        result = 0

        for i in range(len(self.roman)):
            current_value = self.roman_numerals[self.roman[i]]
            if i + 1 < len(self.roman) and self.roman_numerals[self.roman[i + 1]] > current_value:
                result -= current_value
            else:
                result += current_value

        return result

# Example Usage
input_roman_class = "XIV"
roman_numeral = RomanNumeral(input_roman_class)
output_arabic_class = roman_numeral.to_arabic()
print(f"{input_roman_class} in Arabic numerals: {output_arabic_class}")

Output:

XIV in Arabic numerals: 14

In this method, we encapsulate the conversion logic within a class, providing a modular and reusable solution.

Conclusion:

In this blog, we have explored multiple methods to create a Roman numeral converter in Python. We started with a simple approach using a dictionary, and then explored a recursive solution. Finally, we presented an object-oriented approach using a class to encapsulate the conversion logic.

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