29 lines
638 B
PHP
29 lines
638 B
PHP
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<?php
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$numbers = array_map('intval', explode("\n", file_get_contents('input.txt')));
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sort($numbers);
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$difference_of_1 = 0;
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$difference_of_3 = 0;
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$current_jolt = 0;
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while($current_jolt < max($numbers)) {
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if (in_array($current_jolt + 1, $numbers, true)) {
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$current_jolt++;
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$difference_of_1++;
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continue;
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}
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if (in_array($current_jolt + 3, $numbers, true)) {
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$current_jolt += 3;
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$difference_of_3++;
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continue;
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}
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}
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// your device's built-in adapter is always 3 higher than the highest adapter
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$difference_of_3++;
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$current_jolt += 3;
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echo $difference_of_1 * $difference_of_3;
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