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Asked: 2024-09-27T17:29:51+05:30 In: ,

How to Compare Two Roman Numeral Strings for Equality in Python or JavaScript?

I’ve been diving into the fascinating world of Roman numerals lately, and I’ve stumbled upon a challenge that’s been really intriguing. You know how Roman numerals can be a bit convoluted? I mean, figuring out a number represented as “MCMXCIV” really makes you scratch your head. The challenge goes like this: you need to compare two Roman numeral strings and determine if they represent the same value.

Here’s how I visualize it: you get two strings of Roman numerals, say “XII” and “XIII.” Your task is to figure out if they represent the same number. In this case, they don’t, so the output would be false. But how about “X” and “X”? Both represent the number 10, so the output should be true. Pretty straightforward, right?

However, it gets even more interesting when you throw in some edge cases. What if one of the strings is in lowercase, like “xiv” instead of “XIV”? Do you treat them as equal? What if you introduce invalid Roman numerals, like “IIII” or “MMMM”? Should the output be false for those?

I’ve seen a few different approaches in programming languages like Python or JavaScript, but I’m curious to know if anyone’s found a particularly elegant or efficient way to tackle this problem. What algorithms or data structures did you leverage? Did you create a function that directly converts Roman numeral strings into integers, or did you go with a character-by-character comparison?

Also, it would be super helpful if you could share any tips on handling those pesky edge cases, especially for anyone who might be new to working with Roman numerals. I’m really eager to learn from your insights!

So, come on, let’s get some discussion going! How would you approach this problem? What’s your thought process? Feel free to share code snippets or just your general ideas on how to solve this Roman numeral conundrum!

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    2 Answers

    1. Comparing Roman Numerals

      So here’s what I came up with for comparing Roman numerals in a pretty simple way:

      1. First, we need to establish a mapping of Roman numerals to their integer values:

              
        const romanValues = {
            'I': 1,
            'V': 5,
            'X': 10,
            'L': 50,
            'C': 100,
            'D': 500,
            'M': 1000
        };

      2. Then we’ll create a function to convert Roman numerals to integers:

              
        function romanToInt(s) {
            let total = 0;
            let prevValue = 0;

            for (let i = s.length - 1; i >= 0; i--) {
                const currentValue = romanValues[s[i].toUpperCase()] || 0;

                if (currentValue < prevValue) {
                    total -= currentValue; // If the current value is less than the previous, subtract it
                } else {
                    total += currentValue; // Otherwise, add the current value
                }
                prevValue = currentValue; // Update the previous value
            }
            return total;
        }

      3. Now let’s create the function to compare two Roman numeral strings:

              
        function areRomanNumeralsEqual(roman1, roman2) {
            // Convert both Roman numerals to integers
            const num1 = romanToInt(roman1);
            const num2 = romanToInt(roman2);

            // Check if either converted number is invalid (0 means invalid)
            if (num1 === 0 || num2 === 0) {
                return false;
            }

            // Return whether they are equal
            return num1 === num2;
        }

      4. Finally, let’s test our function!

              
        console.log(areRomanNumeralsEqual("XII", "XIII")); // false
        console.log(areRomanNumeralsEqual("X", "X")); // true
        console.log(areRomanNumeralsEqual("XIV", "xiv")); // true
        console.log(areRomanNumeralsEqual("IIII", "IV")); // false (invalid)
        console.log(areRomanNumeralsEqual("MMMM", "MMMM")); // false (invalid)

      Tips for Edge Cases:

      • Always convert to uppercase to handle lowercase inputs.
      • Define what you consider invalid Roman numerals, like "IIII" or "MMMM".
      • Check for any undefined characters against your mapping to catch errors.

      That’s pretty much it! Just a simple way to tackle this Roman numeral comparison. Happy coding!

    2. To tackle the challenge of comparing two Roman numeral strings, the first step is to create a function that converts Roman numerals into integers. This conversion can be done by defining a mapping of Roman numeral characters to their integer values, and then iterating through the input string while applying the rules of Roman numeral subtraction (e.g. IV = 4, where I is subtracted from V). After implementing this function, we can convert both input strings to their integer representations and then simply compare the resulting integers. For example, the strings “XII” and “XIII” would convert to 12 and 13 respectively, thus returning false when compared.

      Next, to address the edge cases mentioned, the algorithm can start by standardizing the input by converting all characters to uppercase, ensuring that “xiv” is treated as equal to “XIV”. For invalid Roman numeral checks, we can implement a validation function that detects invalid sequences (e.g., “IIII” or “MMMM”). If an invalid numeral is detected during conversion, the function returns false immediately. Below is a simple implementation in Python:

      def roman_to_int(s):
    roman_map = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
    total = 0
    previous_value = 0

    for char in reversed(s.upper()):
        value = roman_map.get(char, 0)
        if value == 0:  # Invalid numeral
            return -1
        if value < previous_value:
            total -= value
        else:
            total += value
        previous_value = value

    return total

def compare_roman_numerals(s1, s2):
    return roman_to_int(s1) == roman_to_int(s2)

# Testing the function
print(compare_roman_numerals("XII", "XIII"))  # Output: False
print(compare_roman_numerals("XIV", "xiv"))   # Output: True
print(compare_roman_numerals("IIII", "IV"))   # Output: False

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