多条件循环

Question

Can a do-while loop have multiple conditions? If so, I can't figure out why the code below is failing on all but the first condition.

Functions used...

function gcf($a,$b) {
$a = abs($a); $b = abs($b);
if( $a < $b) list($b,$a) = Array($a,$b);
if( $b == 0) return $a;
$r = $a % $b;
while($r > 0) {
    $a = $b;
    $b = $r;
    $r = $a % $b;
}
return $b;
}


function factors($n){
$factors_array = array();
for ($x = 1; $x <= sqrt(abs($n)); $x++)
{
    if ($n % $x == 0)
    {
        $z = $n/$x; 
        array_push($factors_array, $x, $z);
    }
}
return $factors_array;
}

Code...

$a = $b;

do{
    $a = mt_rand(8, 100);
    $a_factors_array = factors($a);

    $b = mt_rand(8, 100);
    $b_factors_array = factors($b);

} while ($a == $b && count($a_factors_array) < 4 && count($b_factors_array) < 4 && gcf($a, $b) == 1);

echo $a . '<br>';
echo $b . '<br>';

echo count($a_factors_array) . '<br>';
echo count($b_factors_array) . '<br>';

echo gcf($a, $b) . '<br>';

I keep getting numbers for $a and $b that have less than 4 factors and have a GCF of 1. Any ideas?

Answer 1

You'll need || instead of && . You want to repeat the loop as long as any one of your conditions is met. Currently the loop is only repeated if all of the conditions are met.

Answer 2

I think you have an ANDs where you meant an ORs:

do{
    $a = mt_rand(8, 100);
    $a_factors_array = factors($a);

    $b = mt_rand(8, 100);
    $b_factors_array = factors($b);

} while ($a == $b || count($a_factors_array) < 4 || count($b_factors_array) < 4 || gcf($a, $b) == 1);

With your way, the while stops if $a !== $b which is probably not what you want.