53 lines
1.6 KiB
PHP
53 lines
1.6 KiB
PHP
<?php
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$lines = array_map('str_split', explode("\n", file_get_contents('input.txt')));
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$oxygen_lines = $lines;
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for ($i = 0, $l = count($oxygen_lines[0]); $i < $l; $i++) {
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if (count($oxygen_lines) <= 1) {
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break;
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}
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$rotated_lines = array_map('array_reverse', array_map(null, ...$oxygen_lines)); // matrix rotation
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$max = determine_max_number_at_line($rotated_lines, $i);
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$oxygen_lines = array_filter($oxygen_lines, static function ($line) use ($max, $i) {
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return $line[$i] == $max;
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});
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}
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$co2_lines = $lines;
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for ($i = 0, $l = count($co2_lines[0]); $i < $l; $i++) {
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if (count($co2_lines) <= 1) {
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break;
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}
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$rotated_lines = array_map('array_reverse', array_map(null, ...$co2_lines)); // matrix rotation
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$min = determine_min_number_at_line($rotated_lines, $i);
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$co2_lines = array_filter($co2_lines, static function ($line) use ($min, $i) {
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return $line[$i] == $min;
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});
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}
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$oxygen = implode(current($oxygen_lines));
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$co2 = implode(current($co2_lines));
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echo bindec($oxygen) * bindec($co2);
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function determine_max_number_at_line($rotated_lines, $line_number): bool|int|string
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{
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$line = $rotated_lines[$line_number];
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$counts = array_count_values($line);
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if ($counts[0] === $counts[1]) {
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return 1;
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}
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return array_search(max($counts), $counts);
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}
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function determine_min_number_at_line($rotated_lines, $line_number): bool|int|string
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{
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$line = $rotated_lines[$line_number];
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$counts = array_count_values($line);
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if ($counts[0] === $counts[1]) {
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return 0;
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}
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return array_search(min($counts), $counts);
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}
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