PRIMEFACTORS.c

#include <stdio.h>
#include <math.h>

void print_factors(long n);

int main(int argc, char **argv)
{
	long n;
	while (1)
	{
		scanf("%ld", &n);
		if (n==0)
		{
			break;
		}
		printf("%ld = ", n);
		if (n<0)
		{
			printf("-1 x ");
			n = -n;
		}
		print_factors(n);
		printf("\n");
	}
	return 0;
}

void print_factors(long n)
{
	int first = 1;
	while (n%2==0)
	{
		if (first)
		{
			printf("2");
			first = 0;
		}
		else
		{
			printf(" x 2");
		}
		n /= 2;
	}
	long i = 3;
	long sqn = (sqrt(n))+1;
	while (i <= sqn)
	{
		if ((n%i)==0)
		{
			if (first)
			{
				printf("%ld", i);
				first = 0;
			}
			else
			{
				printf(" x %ld", i);
			}
			n /= i;
		}
		else
		{
			i += 2;			
		}
	}
	if (n>1)
	{
		if(first)
		{
			printf("%ld", n);
		}
		else
		{
			printf(" x %ld", n);
		}
	}
}