here is an elegant recursive solution
<?php
function gcd($a,$b) {
return ($a % $b) ? gcd($b,$a % $b) : $b;
}
?>
gmp_gcd
(PHP 4 >= 4.0.4, PHP 5)
gmp_gcd — Calcule le GCD
Description
resource gmp_gcd
( resource
$a
, resource $b
)
Calcule le PGCD (plus grand commun diviseur) de a
et b. Le résultat est toujours positif, même si
l'un des deux (ou les deux) nombres est négatif.
Liste de paramètres
-
a -
Il peut être soit une ressource GMP, soit une chaîne numérique qu'il est possible de convertir plus tard en un nombre.
-
b -
Il peut être soit une ressource GMP, soit une chaîne numérique qu'il est possible de convertir plus tard en un nombre.
Valeurs de retour
Un nombre positif GMP qui se divise avec
a et b.
Exemples
Exemple #1 Exemple avec gmp_gcd()
<?php
$gcd = gmp_gcd("12", "21");
echo gmp_strval($gcd) . "\n";
?>
L'exemple ci-dessus va afficher :
3
add a note
User Contributed Notes 6 notes
bigkm1 at gmail dot com ¶
7 years ago
sean__remove__ at eternalrise_r_emove__ dot com ¶
5 years ago
Here's my solution for getting the GCD of several numbers.
<?php
/*
* function gcd()
*
* returns greatest common divisor
* between two numbers
* tested against gmp_gcd()
*/
function gcd($a, $b)
{
if ($a == 0 || $b == 0)
return abs( max(abs($a), abs($b)) );
$r = $a % $b;
return ($r != 0) ?
gcd($b, $r) :
abs($b);
}
/*
* function gcd_array()
*
* gets greatest common divisor among
* an array of numbers
*/
function gcd_array($array, $a = 0)
{
$b = array_pop($array);
return ($b === null) ?
(int)$a :
gcd_array($array, gcd($a, $b));
}
?>
limas at kultur-online dot at ¶
6 years ago
The previous function returns just 1 under php 5.2.4 but the following seems to work (m>0,n>0):
function gcd($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($_n);
}
scr02001 at student dot mdh dot se ¶
10 years ago
If you do not consier a or b as possible negative numbers, a GCD funktion may return a negative GCD, wich is NOT a greatest common divisor, therefore a funktion like this may be better. This considers the simplyfying of (-3)-(-6) where gcd on -3 and -6 would result in 3, not -3 as with the other function. (-3)-(-6) is (-1)-(-2) NOT (1)-(2)
function eGCD($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 $a;
}
Ludwig Heymbeeck ¶
11 years ago
The following function is more accurate:
function GCD($num1, $num2) {
/* finds the greatest common factor between two numbers */
while ($num2 != 0){
$t = $num1 % $num2;
$num1 = $num2;
$num2 = $t;
}
return $num1;
}
x-empt-php dot net at ispep dot cx ¶
11 years ago
No need to compile gmp functions in just for the GCD function... use this one instead:
function GCD($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;
}
