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31 lines
916 B
PHP
31 lines
916 B
PHP
<?php
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/**
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* The Sieve of Eratosthenes is an algorithm is an ancient algorithm for finding all prime numbers up to any given limit
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* https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
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*
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* @author Michał Żarnecki https://github.com/rzarno
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* @param int $number the limit of prime numbers to generate
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* @return string[] prime numbers up to the given limit
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*/
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function eratosthenesSieve(int $number): array
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{
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$primes = range(1, $number);
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$primes = array_combine($primes, $primes);
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$limit = sqrt($number);
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$current = 2;
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while ($current < $limit) {
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$multiplied = $current;
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$factor = 1;
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while ($multiplied < $number) {
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$factor++;
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$multiplied = $current * $factor;
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if (isset($primes[$multiplied])) {
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unset($primes[$multiplied]);
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}
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}
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$current += 1;
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}
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return array_values($primes);
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}
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