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advent_of_code_2021/03/part2.php
2021-12-03 19:25:51 +01:00

12 lines
424 B
PHP

<?php
$input = file('input', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
$input = array_map(fn($line) => str_split($line), $input);
$gamma = $epsilon = [];
for ($i = 0; $i < count($input[0]); $i++) {
$bit = (int) (array_sum($column = array_column($input, $i)) >= ceil(count($column) / 2));
$gamma[] = $bit;
$epsilon[] = ~$bit & 1;
}
echo bindec(implode('', $gamma)) * bindec(implode('', $epsilon)).PHP_EOL;