gmp_fact
Try...
function gcd($a, $b){
$b = ( $a == 0 )? 0 : $b;
return ( $a % $b )? gcd($b, abs($a - $b)) : $b;
}
always returns positive number even if one or both numbers are negative (as per the gmp_gcd function)
order agnostic, larger number can be $b or $a doesn't matter
also, other examples here were failing when one of the numbers was 0
gmp_gcd
(PHP 4 >= 4.0.4, PHP 5)
gmp_gcd — Calcula el MCD (máximo común divisor)
Descripción
resource gmp_gcd
( resource $a
, resource $b
)
Calcula el divisor comú más grande de a y b . El resultado siempre es positivo, incluso aunque alguno de los parámetros (o los dos) se negativo.
Example #1 Ejemplo de gmp_gcd()
<?php
$mcd = gmp_gcd("12", "21");
echo gmp_strval($mcd) . "\n";
?>
La salida del anterior programa es:
3
add a note
User Contributed Notesgmp_gcd
jim dot mayes at gmail dot com
03-Apr-2008 02:53
03-Apr-2008 02:53
limas at kultur-online dot at
01-Dec-2007 10:44
01-Dec-2007 10:44
The previous function returns just 1 under php 5.2.4 but the following seems to work (m>0,n>0):
function gcd($m,$n)
{
$_m=$m;$r=1;
if($m<$n){$t=$m;$m=$n;$n=$t;}
while($r)
{
$r=(floor($m/$n)*$n)-$m;
$_n=$n;$n=$r;$m=$_m;
}
return abs($_n);
}
bigkm1 at gmail dot com
25-Aug-2006 09:33
25-Aug-2006 09:33
here is an elegant recursive solution
<?php
function gcd($a,$b) {
return ($a % $b) ? gcd($b,$a % $b) : $b;
}
?>
scr02001 at student dot mdh dot se
16-Aug-2003 06:58
16-Aug-2003 06:58
If you do not consier a or b as possible negative numbers, a GCD funktion may return a negative GCD, wich is NOT a greatest common divisor, therefore a funktion like this may be better. This considers the simplyfying of (-3)-(-6) where gcd on -3 and -6 would result in 3, not -3 as with the other function. (-3)-(-6) is (-1)-(-2) NOT (1)-(2)
function eGCD($a,$b){
if($a < 0) $a=0-$a;
if($b < 0 ) $b=0-$b;
if($a == 0 || $b == 0) return 1;
if($a == $b) return a;
do{
$rest=(int) $a % $b; $a=$b; $b=$rest;
}while($rest >0);
return $a;
}
Ludwig Heymbeeck
12-Jan-2003 10:33
12-Jan-2003 10:33
The following function is more accurate:
function GCD($num1, $num2) {
/* finds the greatest common factor between two numbers */
while ($num2 != 0){
$t = $num1 % $num2;
$num1 = $num2;
$num2 = $t;
}
return $num1;
}
x-empt-php dot net at ispep dot cx
06-Jul-2002 11:16
06-Jul-2002 11:16
No need to compile gmp functions in just for the GCD function... use this one instead:
function GCD($num1, $num2) {
/* finds the greatest common factor between two numbers */
if ($num1 < $num2) {
$t = $num1;
$num1 = $num2;
$num2 = $t;
}
while ($t = ($num1 % $num2) != 0) {
$num1 = $num2;
$num2 = $t;
}
return $num2;
}