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<?php function generatePrimesA($n) { $primes = [2]; for ($i = 3; $i < $n; $i += 2) { foreach ($primes as $prime) { if ($i % $prime == 0) { continue 2; } } $primes[] = $i; } return $primes; } function generatePrimesB($n) { $primes = [2]; $lastPrime = 2; for ($i = 3; $i < $n; $i += $lastPrime) { foreach ($primes as $prime) { if ($i % $prime == 0) { continue 2; } } $primes[] = $i; $lastPrime = $i; } return $primes; } var_dump(count(generatePrimesA(1000))); var_dump(count(generatePrimesB(1000))); var_dump(array_diff(generatePrimesA(1000), generatePrimesB(1000)));

preferences:
38.1 ms | 402 KiB | 5 Q