krzysiej/advent_of_code_2021
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kplaczek
2021-12-03 21:32:44 +01:00
parent 6365d1fef7
commit d09dcfb2b4
3 changed files with 32 additions and 18 deletions
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18
03/part2.php
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@@ -2,10 +2,18 @@
$input = file('input', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
$input = array_map(fn($line) => str_split($line), $input);
$gamma = $epsilon = [];
$o2 = $co2 = $input;
for ($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;
if (count($o2) > 1) {
$bit = (int)(array_sum($column = array_column($o2, $i)) >= ceil(count($column) / 2));
$o2 = array_filter($o2, fn($line) => $line[$i] == $bit);
}
if (count($co2) > 1) {
$bit = (int) (array_sum($column = array_column($co2, $i)) >= ceil(count($column) / 2));
$co2 = array_filter($co2, fn ($line) => $line[$i] != $bit);
}
}
echo bindec(implode('', $gamma)) * bindec(implode('', $epsilon)).PHP_EOL;
echo bindec(implode('', reset($co2))) * bindec(implode('', reset($o2))); //2990784