Converting Decimal Numbers to Roman Numerals

Environment: C, Visual C++

The following function takes positive decimal numbers from 0–4999 and outputs them as Roman strings (for example, "MMIII" for 2003). It should compile under any version of C on any platform (although you may want to change "//" comments to the "/*...*/" form (which I hate).

I wrote the function myself, and I have no copyright concerns. I searched the CodeGuru site for "roman" and got nothing except font names, so I assume noone else has posted anything similar to this.

// written by Ste Cork, free for any and all use.
//
const char *Number_AsRomanString( int iNumber )
{
struct RomanDigit_t
  {
char *m_psString;
int m_iValue;
  };

static const RomanDigit_t RomanDigits[]=
  {
    {"M",  1000},
    {"CM",  900},
    {"D",   500},
    {"CD",  400},
    {"C",   100},
    {"XC",   90},
    {"L",    50},
    {"XL",   40},
    {"X",    10},
    {"IX",    9},
    {"V",     5},
    {"IV",    4},
    {"I",     1},
  };

// Strictly speaking, Roman digits can't display something
// such as 4999 without using overlaid bars and so forth,
// but for now this is a quick-and-dirty piece of code that'll
// just keep using M's...
//
static char sRomanString[20];
sRomanString[0] = '\0';

for (int i=0; iNumber && i<sizeof(RomanDigits)/
                           sizeof(RomanDigits[0]); i++)
  {
while ( RomanDigits[i].m_iValue <= iNumber )
    {
strcat( sRomanString, RomanDigits[i].m_psString );
iNumber -= RomanDigits[i].m_iValue;
    }
  }

return sRomanString;
}


Comments

  • *why* do people use roman numerals?

    Posted by Legacy on 07/29/2003 12:00am

    Originally posted by: njkayaker


    The roman empire is dead! Get over it.

    I really think roman numerals is something that should go away.

    Reply
  • Nice try.

    Posted by Legacy on 07/29/2003 12:00am

    Originally posted by: felix

    You only solved half of the problem. How about converting a roman numeral to a long? problem is starting to get a little harder now isn't it.

    Also, using your scheme, one million is basically 1000 M's.

    I realize that you do not support the *bar* notation, but it would have to be taken into account so that you solution could be useful.

    I would use long instead of int.


    -f

    Reply
Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • On-demand Event Event Date: May 18, 2015 While the idea of using facial and/or gesture recognition to create a modern, intuitive game seems attractive, some developers may want to leverage Unity 3D as a way to accelerate their development efforts. There are many different ways in which Intel and Unity Technologies have been working together to help speed the development of games with the Intel&reag; RealSense™ SDK (software developer kit). Check out this webcast to join a panel of experts as they …

  • On-Demand eSeminar DevOps and Cloud are all the rage in IT, but the two terms relating process and computing aren't mutually exclusive. Join us to see how your movement into cloud changes the way you develop, deploy, test and manage, and how DevOps can actually be a good thing when coupled with cloud.

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date