23 lines
419 B
PHP
23 lines
419 B
PHP
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<?php
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define('MAX',10000);
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function d($int) {
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static $cache;
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if(isset($cache[$int])) {return $cache[$int]; }
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$sum = 0;
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for($n=1;$n<$int;$n++) {
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if($int % $n == 0)
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$sum += $n;
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}
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$cache[$int] = $sum;
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return $sum;
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}
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$result = 0;
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for($number = 1; $number < MAX; $number++) {
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$d_sum = d($number);
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if($number != $d_sum AND $number == d($d_sum)) {
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$result += $number;
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}
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}
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echo $result;
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