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  • Your email address will not be published.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

  • Live Event Date: September 23, 2015 @ 1:00 p.m. ET / 10:00 a.m. PT The cloud is not just about a runtime platform for your projects – now, you can do your development in the cloud, too. Check out this upcoming eseminar to learn how the cloud improves your development experience and team collaboration. Join Dana Singleterry, Principal Product Manager for Oracle Dev Tools, as he discusses how to simplify every aspect of the development lifecycle, including requirements gathering, version management, code …

  • When individual departments procure cloud service for their own use, they usually don't consider the hazardous organization-wide implications. Read this paper to learn best practices for setting up an internal, IT-based cloud brokerage function that service the entire organization. Find out how this approach enables you to retain top-down visibility and control of network security and manage the impact of cloud traffic on your WAN.

Most Popular Programming Stories

More for Developers

RSS Feeds

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