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 — 最大公約数を計算する
説明
resource gmp_gcd ( resource a, resource b )a と b の最大公約数を 計算します。引数のどちらかまたは両方が負の場合でも結果は常に 正となります。
例 735. gmp_gcd() の例
<?php
$gcd = gmp_gcd("12", "21");
echo gmp_strval($gcd) . "\n";
?>
上のプログラムの出力は以下のようになります。
3
gmp_gcd
bigkm1 at gmail dot com
26-Aug-2006 01:33
26-Aug-2006 01:33
scr02001 at student dot mdh dot se
16-Aug-2003 10:58
16-Aug-2003 10:58
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 $a;
}
Ludwig Heymbeeck
13-Jan-2003 03:33
13-Jan-2003 03:33
The following function is more accurate:
function GCD($num1, $num2) {
/* finds the greatest common factor between two numbers */
while ($num2 != 0){
$t = $num1 % $num2;
$num1 = $num2;
$num2 = $t;
}
return $num1;
}
x-empt-php dot net at ispep dot cx
07-Jul-2002 03:16
07-Jul-2002 03:16
No need to compile gmp functions in just for the GCD function... use this one instead:
function GCD($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;
}