34 lines
867 B
PHP
34 lines
867 B
PHP
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<?php
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$count = 0;
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$sum = 0;
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function is_prime(int $n) :bool{for($i=$n**.5|1;$i&&$n%$i--;);return!$i&&$n>1;}
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for ($prime = 11; $count < 11; $prime += 2) {
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if (is_prime($prime)) {
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//echo "Testing $prime\n";
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for ($c = 1; $c < strlen($prime); $c++) {
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$left = substr($prime, -$c);
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//echo "Trimmed left $left\n";
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if (!is_prime($left)) {
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//echo "Not prime $left\n";
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continue 2;
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}
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}
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for ($c = 1; $c < strlen($prime); $c++) {
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$right = substr($prime, 0, $c);
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//echo "Trimmed right $right\n";
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if (!is_prime($right)) {
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//echo "Not prime $right\n";
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continue 2;
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}
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}
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$sum += $prime;
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$count++;
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echo "found $prime\n";
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}
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}
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echo "Total sum: $sum\n";
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