private bool checkSubstract2(string s)
{
int length = s.Length;
if (length <= 2)
{
return(true);
}
else
{
// Check substring of length 3
for (int i = 2; i < length; i++)
{
RomanSymbol current = new RomanSymbol(s[i]);
RomanSymbol currentMinus1 = new RomanSymbol(s[i - 1]);
RomanSymbol currentMinus2 = new RomanSymbol(s[i - 2]);
if (current.GetValue() > currentMinus1.GetValue() && current.GetValue() > currentMinus2.GetValue())
{
return(false);
}
}
}
return(true);
}
private bool checkSubstractPattern(string s)
{
// Rules:
// "I" can be subtracted from "V" and "X" only
// "X" can be subtracted from "L" and "C" only.
// "C" can be subtracted from "D" and "M" only.
// "V", "L", and "D" can never be subtracted.
char[] input = s.ToArray();
char[] substractable = { 'I', 'X', 'C' };
for (int i = 0; i < s.Length - 1; i++)
{
char current = input[i];
RomanSymbol currentS = new RomanSymbol(current);
char next = input[i + 1];
RomanSymbol nextS = new RomanSymbol(next);
if (substractable.Contains(current))
{
// small values can only be substracted from values <= 10 times of itself
if (nextS.GetValue() > currentS.GetValue() * 10)
{
return(false);
}
}
else
{
// "V", "L", and "D" can never be subtracted.
if (currentS.GetValue() < nextS.GetValue())
{
return(false);
}
}
}
return(true);
}