RomanNumber.c

/*************************************************************************
参考資料
http://ja.wikipedia.org/wiki/%E3%83%AD%E3%83%BC%E3%83%9E%E6%95%B0%E5%AD%97
**************************************************************************/
#include <assert.h>
#include <stdio.h>
#include <string.h>

int arabic_to_roman(int arabic, char *roman);
int check(int arabic, const char *roman);

int main(void)
{
	assert(check(  11, "XI"));
	assert(check(  12, "XII"));
	assert(check(  14, "XIV"));
	assert(check(  18, "XVIII"));
	assert(check(  24, "XXIV"));
	assert(check(  43, "XLIII"));
	assert(check(  99, "XCIX"));
	assert(check( 495, "CDXCV"));
	assert(check(1888, "MDCCCLXXXVIII"));
	assert(check(1945, "MCMXLV"));
	assert(check(3999, "MMMCMXCIX"));
	
	assert(!check(-1, ""));
	assert(!check(4000, ""));

	return (0);
}

int check(int arabic, const char *roman)
{
	char roman_number[64];
	if (arabic_to_roman(arabic, roman_number)){
		return (0);
	}
	return (strcmp(roman_number, roman) == 0);
}

#define ROMAN_NUMBER     ("IVXLCDM")
#define ROMAN_STACK_SIZE (64)
#define ROMAN_NUMBER_MAX (3999)
#define ROMAN_NUMBER_MIN (1)
#define STACK_PUSH(val)  roman_stack[roman_stack_index++] = (val)
#define STACK_POP        roman_stack[--roman_stack_index]
#define IS_EMPTY         (roman_stack_index == 0)

int arabic_to_roman(int arabic, char *roman)
{
	char roman_stack[ROMAN_STACK_SIZE];
	int  roman_stack_index;
	int  counter;

	if (ROMAN_NUMBER_MIN > arabic || arabic > ROMAN_NUMBER_MAX){
		fprintf(stderr, "roman number [%d, %d]\n", ROMAN_NUMBER_MIN, ROMAN_NUMBER_MAX);
		return (1);
	}

	roman_stack_index = 0;
	counter = 0;
	while (arabic > 0){
		int n, i;
		n = arabic % 10;
		if (n < 4){
			for (i = 0; i < n; i++) STACK_PUSH(ROMAN_NUMBER[counter]);
		}
		else if (n == 4){
			STACK_PUSH(ROMAN_NUMBER[counter + 1]);
			STACK_PUSH(ROMAN_NUMBER[counter]);
		}
		else if (n < 9){
			for (i = 0; i < n - 5; i++) STACK_PUSH(ROMAN_NUMBER[counter]);
			STACK_PUSH(ROMAN_NUMBER[counter + 1]);
		}
		else {
			STACK_PUSH(ROMAN_NUMBER[counter + 2]);
			STACK_PUSH(ROMAN_NUMBER[counter]);
		}
		arabic /= 10;
		counter += 2;
	}

	while (!IS_EMPTY){
		*(roman++) = STACK_POP;
	}
	*roman = '\0';

	return (0);
}

#undef ROMAN_NUMBER
#undef ROMAN_NUMBER_MAX
#undef ROMAN_NUMBER_MIN
#undef ROMAN_STACK_SIZE
#undef STACK_PUSH
#undef STACK_POP
#undef IS_EMPTY