Converting Decimal Numbers to Roman Numerals using Java and Python

Roman numerals are a numeral system that originated in ancient Rome and remained the usual way of writing numbers throughout Europe well into the Late Middle Ages. In this blog post, we will discuss a simple algorithm to convert decimal numbers to their equivalent Roman numerals. We will provide examples in both Java and Python.

The Algorithm

The algorithm for converting decimal numbers to Roman numerals involves the following steps:

1. Create a list of Roman numerals and their corresponding decimal values. The list should be ordered from highest to lowest. For example, M=1000, CM=900, D=500, CD=400, C=100, XC=90, L=50, XL=40, X=10, IX=9, V=5, IV=4, I=1.
2. Start from the highest Roman numeral (M=1000). For each numeral, as long as the given number is greater than or equal to the value of the numeral, subtract the value of the numeral from the number and append the numeral to the result.
3. Repeat step 2 until the number becomes 0. The result will be the Roman numeral representation of the given number.

Java Implementation

Here is a simple Java implementation of the above algorithm:

public class DecimalToRoman {
    private static final int[] VALUES = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
    private static final String[] SYMBOLS = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};

    public static String decimalToRoman(int num) {
        StringBuilder roman = new StringBuilder();
        for (int i = 0; i < VALUES.length && num > 0; i++) {
            while (VALUES[i] <= num) {
                num -= VALUES[i];
                roman.append(SYMBOLS[i]);
            }
        }
        return roman.toString();
    }
}

Python Implementation

Here is a simple Python implementation of the above algorithm:

def decimal_to_roman(num):
    values = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1]
    symbols = ["M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"]
    roman = ''
    for i in range(len(values)):
        while num >= values[i]:
            num -= values[i]
            roman += symbols[i]
    return roman

Conclusion

Converting decimal numbers to Roman numerals is a common problem that can be solved using a simple algorithm. The above Java and Python implementations demonstrate how to use this algorithm to convert any decimal number to its equivalent Roman numeral. Happy coding!