function q4()
{
$highestPalindrome = null;
for ($i = 999; $i > 99; --$i) {
for ($j = 999; $j > 99; --$j) {
$value = $i * $j;
if ($value < $highestPalindrome) {
break;
}
if (Str::isPalindrome($value)) {
$highestPalindrome = $value;
}
}
}
return $highestPalindrome;
}
function q35($max)
{
$primes = Prime::upTo($max);
$primes = array_flip($primes);
$circularPrimesCount = 0;
foreach ($primes as $prime => $dontCare) {
$length = strlen($prime);
$isCircular = true;
for ($i = 0; $i < $length; ++$i) {
$rotatedPrime = Str::rotate($prime, $i);
if (!isset($primes[$rotatedPrime])) {
$isCircular = false;
break;
}
}
if ($isCircular) {
++$circularPrimesCount;
}
}
return $circularPrimesCount;
}
