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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