/* Exercise 4.12 from "The C programming language" book by K&R */

#include <stdio.h>
#include <string.h>

void reverse(char s[])
{
	int c, i, j;
	for (i = 0, j = strlen(s)-1; i < j; i++, j--) {
		c = s[i];
		s[i] = s[j];
		s[j] = c;
	}
}

/* recursive version of itoa() */
void itoa_r(char n, char s[])
{
	static int i;
	static int sign;
	
	if (i == 0)
		if ((sign = n) < 0)
			n = -n;
	s[i++] = n % 10 + '0';
	if ((n /= 10) > 0)
		itoa_r(n,s);	
	else {
		if (sign < 0) {
			s[i++] = '-';
			sign = 0;
		}
		s[i] = '\0';
	}
}

int main(void)
{
	char s[100] = "";
	itoa_r(-123,s);
	reverse(s);
	printf("%s\n",s);
	return 0;
}