/* We need standard IO */
**#include** <stdio.h>
/* We need an integer square root */
**#include** "isqrt.c"
/* factor a number by Halleck's method. Generating relation that */
/* generated this was N = pq =(S-A)(S+B) where S is the integer */
/* Square root. */
main () {
long n, p, q, s, t;
printf ("Factor a positive number by Halleck's method\n");
printf ("N = \n"); scanf ("%ld", &n);
printf ("Factoring %ld\n", n);
if (n<1) { printf ("N must be greater than zero\n"); return 1;}
s = isqrt(n);
p = s; q = s; t = p*q - n;
while (t!=0) if (t<0) { t += p; q++; }
else { t -= q; p--; }
printf ("%ld*%ld=%ld\n",p,q,n);
}

# Go to ...

This page is http://www.cc.utah.edu/~nahaj/factoring/halleck.c.html
© Copyright 2003 by John Halleck, All Rights Reserved.
This snapshot was last modified on December 24th, 2013