Roman to Integer

Roman numerals, originating from ancient Rome, utilize combinations of Latin letters to represent values:

• I = 1
• V = 5
• X = 10
• L = 50
• C = 100
• D = 500
• M = 1000

Typically, numerals are written from largest to smallest from left to right. However, to represent numbers like 4 and 9, a subtractive notation is used, where a smaller numeral precedes a larger one, indicating subtraction. For example, IV represents 4 (5 - 1), and IX represents 9 (10 - 1).
MEDIUM

To convert a Roman numeral to an integer, follow these steps:

1. Initialize a total sum to zero.
2. Traverse the Roman numeral from left to right.
3. For each symbol:

• If its value is less than the value of the next symbol, subtract it from the total.
• Otherwise, add its value to the total.

This method accounts for both additive and subtractive combinations in Roman numerals.

For example, to convert "MCMXCIV" to an integer:

1. M (1000)
2. CM (900)
3. XC (90)
4. IV (4)

Adding these values together: 1000 + 900 + 90 + 4 = 1994.

This approach ensures accurate conversion of Roman numerals to their integer equivalents.

Example 1
`
using System;
class Program
{
static void Main()
{
string roman = "MCMXCIV"; // Example Roman numeral
int result = RomanToInt(roman);
Console.WriteLine($"The integer value of {roman} is {result}.");
}

static int RomanToInt(string s)
{
    int total = 0;
    int prevValue = 0;

    foreach (char c in s)
    {
        int currentValue = RomanCharToValue(c);

        if (currentValue > prevValue)
        {
            // Subtract twice the previous value since it was added earlier
            total += currentValue - 2 * prevValue;
        }
        else
        {
            total += currentValue;
        }

        prevValue = currentValue;
    }

    return total;
}

static int RomanCharToValue(char c)
{
    switch (c)
    {
        case 'I': return 1;
        case 'V': return 5;
        case 'X': return 10;
        case 'L': return 50;
        case 'C': return 100;
        case 'D': return 500;
        case 'M': return 1000;
        default: throw new ArgumentException("Invalid Roman numeral character");
    }
}

}

`

Example 2
`
class RomanToInt {
public static int _RomanToInt(string s)
{
int total = 0, prevValue = 0, currentValue = 0;

    for (int i = s.Length - 1; i >= 0; i--)
    {
        switch (s[i])
        {
            case 'I':  currentValue =  1; break;;
            case 'V': currentValue =  5; break;;
            case 'X': currentValue =  10; break;;
            case 'L': currentValue =  50; break;;
            case 'C': currentValue =  100; break;;
            case 'D': currentValue =  500; break;;
            case 'M': currentValue =  1000; break;;
            default: throw new ArgumentException("Invalid Roman numeral character");
        }
        total = (currentValue > prevValue) ? (total + currentValue) : total - currentValue;
        prevValue = currentValue;
    }

    return total;
}

}

`

Thanks for Reading.