47 lines
1.4 KiB
C
47 lines
1.4 KiB
C
#include <stdio.h>
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int digits[26] = { 0, 0, 100, 500, 0, 0, 0, 0, 1, 1, 0, 50, 1000, 0, 0, 0, 0, 0, 0, 0, 5, 5, 0, 10, 0, 0 };
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/* assuming ASCII, do upper case and get index in alphabet. could also be
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inline int VALUE(char x) { return digits [ (~0x20 & x) - 'A' ]; }
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if you think macros are evil */
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#define VALUE(x) digits[(~0x20 & (x)) - 'A']
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int decode(const char * roman)
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{
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const char *bigger;
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int current;
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int arabic = 0;
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while (*roman != '\0') {
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current = VALUE(*roman);
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/* if (!current) return -1;
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note: -1 can be used as error code; Romans didn't even have zero
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*/
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bigger = roman;
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/* look for a larger digit, like IV or XM */
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while (VALUE(*bigger) <= current && *++bigger != '\0');
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if (*bigger == '\0')
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arabic += current;
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else {
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arabic += VALUE(*bigger);
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while (roman < bigger)
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arabic -= VALUE(* (roman++) );
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}
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roman ++;
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}
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return arabic;
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}
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int main()
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{
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const char * romans[] = { "MCmxC", "MMVIII", "MDClXVI", "MCXLUJ" };
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int i;
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for (i = 0; i < 4; i++)
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printf("%s\t%d\n", romans[i], decode(romans[i]));
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return 0;
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}
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