Roman Numerals

roman.c

 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
  
 struct symbol_table {
	int num;
	char sym[3];
 };
 
 struct symbol_table symbols[] = {
	{1000,  "M"},
	{900,   "CM"},
	{500,   "L"},
	{400,   "CD"},
	{100,   "C"},
	{90,    "XC"},
	{50,    "L"},
	{40,    "XL"},
	{10,    "X"},
	{9,     "IX"},
	{5,     "V"},
	{4,     "IV"},
	{1,     "I"}
 };
 
 int 
 roman_to_arabic(const char *s) 
 {
	int total, num, s_len, p_len;
	struct symbol_table *sym;
	char buf[3];
	char *p;
	
	s_len = strlen(s);
	p = (char *) s;
	p_len = 2;
	total = 0;
		
	while (p < s+s_len) {   
		num = 0;        
		strncpy(buf, p, p_len);
		buf[p_len] = '\0';
		
		/* check if the symbol is in the table */
		for(sym=symbols; sym<symbols+13 && !num; sym++) {
			if (strcmp(buf, sym->sym) == 0)
				num = sym->num;
		}
		
		if (num) {
			/* we found a symbol */
			total += num;
			p += p_len;
			p_len = 2;                      
			continue; 
		} else if (--p_len == 0) {
			/* didn't find a symbol, move to the next one */
			printf("invalid symbol! %s\n", buf);
			p_len = 2;
			p++;
		}

	}
	
	return total;
 }
 
 void
 arabic_to_roman(int d, char *buf) 
 {
 
	struct symbol_table *sym;       
	buf[0] = '\0';
		
	while (d > 0) {         
		for(sym=symbols; sym<symbols+13; sym++) {
			if (d >= sym->num) {
				strcat(buf, sym->sym);
				d -= sym->num;
				break;
			}
		}
	}
 }
 
 int
 main(int argc, char** argv)
 {
	char buf[50];
	int i;
	
	for (i=1; i<=3999; i++) {               
		arabic_to_roman(i, buf);
		printf("%5d -> %-20s", i, buf);
		printf("%s -> %d\n", buf, roman_to_arabic(buf));
	}       
	
	return 0;
 }