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A roman numbers conversion (tested and working)

function to convert unsigned ints into roman numbers, extensible (i just dunno about letter to use when number is 5000 or something, so i stuck with 1000 (roman M)). Syntax of roman numbers are described here: http://www.python.org/dev/peps/pep-0313/

Submitted By: temporary

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Views: 2,125

Language: C

Last Modified: April 25, 2007

Instructions: see main() function about how to use. also, you can extend arrays to get greater roman literals support.

Snippet

/*
Idea to write and post this code born after http://www.dreamincode.net/code/snippet832.htm wrong code review
*/
#include <stdio.h>
unsigned int roman_ranges[] = { 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1, 0 };
unsigned int roman_addsin[] = {-1000, +100, -500, +100, -100, +10, -50, +10, -10, +1, -5, +1, -1, 0 };
char roman_letters[] = { 'M', 'C', 'D', 'C', 'C', 'X', 'L', 'X', 'X', 'I', 'V', 'I', 'I', 0 };
size_t find_index(unsigned int li) {
unsigned int *roman_ranges_ptr = roman_ranges;
while (*roman_ranges_ptr && li < *roman_ranges_ptr) {
++roman_ranges_ptr;
}
return roman_ranges_ptr - roman_ranges;
}
char* uint2roman(unsigned int li, char* buf, size_t bufsize) {
size_t index;
if (bufsize < 1) {
return NULL; // buffer size is not enough for convertion
}
if ( (*buf = roman_letters[ (index = find_index(li)) ]) ) {
return uint2roman(li + roman_addsin[index], buf+1, bufsize-1);
}
return buf;
}
#define ROMAN_NUMBER_BUF_SIZE 64
int main() {
unsigned int nr;
char roman_str[ROMAN_NUMBER_BUF_SIZE];
printf("%s", "Enter an integer: ");
scanf("%lu", &nr);
if (uint2roman(nr, roman_str, ROMAN_NUMBER_BUF_SIZE)) {
printf("Your roman number is %s\n", roman_str);
} else {
printf("%s", "Bad roman number or buffer size too small\n");
}
}

Copy & Paste

/*
Idea to write and post this code born after http://www.dreamincode.net/code/snippet832.htm wrong code review
*/
#include <stdio.h>

unsigned int  roman_ranges[] = { 1000,  900,  500,  400,  100,  90,  50,  40,  10,  9,   5,   4,   1,  0 };
unsigned int  roman_addsin[] = {-1000, +100, -500, +100, -100, +10, -50, +10, -10, +1,  -5,  +1,  -1,  0 };
char         roman_letters[] = { 'M',   'C',  'D',  'C',  'C', 'X', 'L', 'X', 'X', 'I', 'V', 'I', 'I', 0 };

size_t find_index(unsigned int li) {
    unsigned int *roman_ranges_ptr = roman_ranges;
    while (*roman_ranges_ptr && li < *roman_ranges_ptr) {
        ++roman_ranges_ptr;
    }
    return roman_ranges_ptr - roman_ranges;
}

char* uint2roman(unsigned int li, char* buf, size_t bufsize) {
    size_t index;
    if (bufsize < 1) {
        return NULL; // buffer size is not enough for convertion
    }
    if ( (*buf = roman_letters[ (index = find_index(li)) ]) ) {
        return uint2roman(li + roman_addsin[index], buf+1, bufsize-1);
    }
    return buf;
}

#define ROMAN_NUMBER_BUF_SIZE 64
int main() {
    unsigned int nr;
    char roman_str[ROMAN_NUMBER_BUF_SIZE];

printf("%s", "Enter an integer: ");
    scanf("%lu", &nr);
    if (uint2roman(nr, roman_str, ROMAN_NUMBER_BUF_SIZE)) {
        printf("Your roman number is %s\n", roman_str);
    } else {
        printf("%s", "Bad roman number or buffer size too small\n");
    }
}