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Groups > comp.lang.c > #15789

factor

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


int main(int argc, char **argv)
{
    const char *arg;
    unsigned long ori;
    unsigned long red;
    unsigned long div;
    unsigned long ste;

    if (argc != 2)
    {
	fputs("usage: factor <number>\n", stderr);
	return 1;
    }

    arg = argv[1];
    sscanf(arg, "%lu", &ori);
    red = ori;
    fprintf(stdout, "%lu", ori);
    fputs(" = ", stdout);

    if (red < 4)
    {
	fputc('0' + (int) red, stdout);
	goto done;
    }

    if ((red & 0x1) == 0x0)
    {
	red >>= 1;
	fputc('2', stdout);

	if ((red & 0x1) == 0x0)
	{
	    int x;

	    fputc('^', stdout);
	    red >>= 1;
	    x = 2;

	    while ((red & 0x1) == 0x0)
	    {
		red >>= 1;
		x++;
	    }

	    fprintf(stdout, "%d", x);
	}

	if (red == 1)
	    goto done;

	fputc('*', stdout);
    }

    if (red % 3 == 0)
    {
	fputc('3', stdout);
	red /= 3;

	if (red % 3 == 0)
	{
	    int x;

	    red /= 3;
	    fputc('^', stdout);
	    x = 2;

	    while (red % 3 == 0)
	    {
		red /= 3;
		x++;
	    }

	    fprintf(stdout, "%d", x);
	}

	if (red == 1)
	    goto done;

	fputc('*', stdout);
    }

    div = 5;
    ste = 2;

    for (;;)
    {
	unsigned long lim;

    relim:
	lim = (unsigned long) floor(sqrt((double) red));

	for (;;)
	{
	    if (red % div == 0)
	    {
		red /= div;
		fprintf(stdout, "%lu", div);

		if (red % div == 0)
		{
		    int x;

		    fputc('^', stdout);
		    red /= div;
		    x = 2;

		    while (red % div == 0)
		    {
			red /= div;
			x++;
		    }

		    fprintf(stdout, "%d", x);
		}

		if (red == 1)
		    goto done;

		fputc('*', stdout);
		goto relim;
	    }

	    div += ste;
	    ste ^= 6;

	    if (div > lim)
	    {
		fprintf(stdout, "%lu", red);
		goto done;
	    }
	}
    }

  done:
    fputc('\n', stdout);
    fflush(stdout);
    return 0;
}

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