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31 lines
416 B
PHP
31 lines
416 B
PHP
<?php
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/**
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* Problem:
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*
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* The prime factors of 13195 are 5, 7, 13 and 29.
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*
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* What is the largest prime factor of the number 600851475143?
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*
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*
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* Answer:
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*
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* 6857
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*
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*
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* @link https://projecteuler.net/problem=3
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*/
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function problem3(): int
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{
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$n = 600851475143;
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$i = 2;
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while ($i * $i < $n) {
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while ($n % $i == 0) {
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$n /= $i;
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}
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$i++;
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}
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return $n;
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}
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