private static int IncrementOrResetRepeatCount(int repeat, RomanCharacter current, RomanCharacter next)
{
return current.Value == next.Value ? repeat + 1 : 1;
}
private static string RomanNumeralForNumber(int number, RomanCharacter romanCharacter)
{
int digit = PlaceValueForRomanNumeral(number, romanCharacter);
if (digit == 9)
return String.Concat(romanCharacter.Character, romanCharacter.TenOfThese.Character);
if (digit == 4)
return String.Concat(romanCharacter.Character, romanCharacter.FiveOfThese.Character);
string roman = "";
if (digit >= 5)
{
roman = romanCharacter.FiveOfThese.Character.ToString();
digit -= 5;
}
roman += new string(romanCharacter.Character, digit);
return roman;
}
private static int ShouldAddOrSubtractTheCurrentValue(RomanCharacter current, RomanCharacter prevCharacter)
{
if (prevCharacter == null)
return 1;
return prevCharacter.Decrementor == current ? -1 : 1;
}
/// <summary>
/// Return the digit for a place value; for instance, for Roman Numeral C (100)
/// and number 3214, return 2 (the hundred's place)
/// </summary>
private static int PlaceValueForRomanNumeral(int number, RomanCharacter roman)
{
int digit = number%(roman.Value*10)/roman.Value;
if (digit < 0 || digit > 10)
throw new ArithmeticException("digit must be between 0 and 9 inclusive");
return digit;
}
private static bool NextIsValidRegular(RomanCharacter current, RomanCharacter next, RomanCharacter maxSoFar)
{
return next.Value >= current.Value && next.Value >= maxSoFar.Value;
}
private static bool NextIsValidDecrement(RomanCharacter current, RomanCharacter next, RomanCharacter previous, int repeat)
{
var prevValue = previous == null ? 0 : previous.Value;
bool currentDecrements = current.Value < prevValue;
bool nextDecrements = next.Value < current.Value;
if (nextDecrements && currentDecrements)
return false;
bool nextIsValidDecrement =
nextDecrements
&& next.Value == current.Decrementor.Value
&& repeat == 1
;
return nextIsValidDecrement;
}
private static bool IsCurrentValueValid(RomanCharacter current, RomanCharacter next, RomanCharacter previous, RomanCharacter maxSoFar, int repeat)
{
if (NextIsValidDecrement(current, next, previous, repeat))
return true;
if (NextIsValidRegular(current, next, maxSoFar))
return true;
return false;
}
private static void Init()
{
I = new RomanCharacter { Character = 'I', Value = 1, Decrementor = null };
V = new RomanCharacter { Character = 'V', Value = 5, Decrementor = I };
X = new RomanCharacter { Character = 'X', Value = 10, Decrementor = I };
L = new RomanCharacter { Character = 'L', Value = 50, Decrementor = X };
C = new RomanCharacter { Character = 'C', Value = 100, Decrementor = X };
D = new RomanCharacter { Character = 'D', Value = 500, Decrementor = C };
M = new RomanCharacter { Character = 'M', Value = 1000, Decrementor = C };
I.FiveOfThese = V;
I.TenOfThese = X;
X.FiveOfThese = L;
X.TenOfThese = C;
C.FiveOfThese = D;
C.TenOfThese = M;
Symbols = new Dictionary<char, RomanCharacter>
{
{I.Character, I},
{V.Character, V},
{X.Character, X},
{L.Character, L},
{C.Character, C},
{D.Character, D},
{M.Character, M}
};
}