stdin to stdout

[leahw25]

I'm a complete novice at c programming. I was wondering what would be the best way to read in roman numerals and convert them into decimal values. I tried the switch statement but it told me that the case label does not reduce to an integer constant when the case was more than two characters.

[D_C]

Do them one character at a time.

// Suppose the string that holds MC...VI is named RN.
while RN is not empty
{
  switch the first character of the string RN
  {
    convert it to it's integer form (case 'M': value = 500; break; // etc.)
  }
  if the previous character is less than current character
  {
    subtract previous character instead of add (total -= (2*prevVal);)
  }
  add the value to the total (total += value;)
  assign value to prevVal;
  remove the first character from string RN
}

[leahw25]

thankyou, it was fantastic. Would it be the same in the reverse order (ie decimal to roman numeral) or would the code be different (ie. finding the place value of the digits)

[D_C]

After reviewing the rules, yeah, take as big of a chunk as you can. The rules aren't exactly clear, but there should be some scheme for uniqueness.

Rules I would use:
- Use as few numerals as possible
- Only subtract (put a smaller number before a larger one) if it's less than some percentage of the bigger number's value. Some say 10% is the cutoff. That is exactly two roman numerals before the current one. That would mean 40 = XXXX instead of XL, and 400 = CCCC instead of CD.
- For numbers considerably larger than M (1000), notations can be used to multiply each number by 1000, or even 1,000,000. That exists for all numbers except I because I * 1000 = M.

For example, 947= (1000 - 100) + (50 - 5) + (2) = CMVLII