105 lines
2.8 KiB
PHP
105 lines
2.8 KiB
PHP
<?php
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[$instructions, $mine, $others] = explode("\n\n", file_get_contents('input.txt'));
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// parse instructions
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function parseInstructions($instructions): array
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{
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// for example : « class: 1-3 or 5-7 »
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preg_match_all('/^([a-z ]+): (\d+)-(\d+) or (\d+)-(\d+)$/mi', $instructions, $matches);
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if (count($matches) !== 6) {
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echo sprintf('Regex failed : %s', var_export($matches, true));
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exit;
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}
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$compares = [];
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array_shift($matches);
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for ($i = 0, $l = count($matches[0]); $i < $l; $i++) {
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$compares[$matches[0][$i]] = static function ($number) use ($matches, $i) {
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$comparison = ($number >= (int)$matches[1][$i] and $number <= (int)$matches[2][$i])
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|| ($number >= (int)$matches[3][$i] and $number <= (int)$matches[4][$i]);
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if ($comparison === true) {
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return true;
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}
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return $number;
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};
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}
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return $compares;
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}
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$compares = parseInstructions($instructions);
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// check valid others
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$others = explode("\n", $others);
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array_shift($others);
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$others = array_map(static function($other) {
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return explode(',', $other);
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}, $others);
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// filter by valid tickets
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$valid_tickets = [];
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foreach ($others as $other) {
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$is_valid = 0;
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foreach ($other as $number) {
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foreach ($compares as $compare) {
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if ($compare((int)$number) === true) {
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$is_valid++;
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break;
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}
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}
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}
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if ($is_valid === 20) {
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$valid_tickets[] = $other;
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}
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}
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// filter columns by what they CAN'T be
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$cant_be = [];
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foreach ($valid_tickets as $valid_ticket) {
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foreach ($valid_ticket as $row => $number) {
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foreach ($compares as $name => $compare) {
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if ($compare((int)$number) !== true) {
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if (
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!array_key_exists($row, $cant_be) ||
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(array_key_exists($row, $cant_be) && !in_array($name, $cant_be[$row], true))
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) {
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$cant_be[$row][] = $name;
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}
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}
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}
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}
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}
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$columns = [];
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$labels = array_keys($compares);
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uasort($cant_be, static function($a, $b) {
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return count($a) >= count($b) ? -1 : 1;
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});
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// label columns
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foreach ($cant_be as $row => $labels_cant_be) {
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foreach ($labels as $i => $label_cant_be) {
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if (!in_array($label_cant_be, $labels_cant_be, true)) {
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$columns[$row] = $label_cant_be;
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unset($labels[$i]);
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break;
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}
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}
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}
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ksort($columns);
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// compare to mine
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$mine = explode("\n", $mine);
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array_shift($mine);
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$mine = explode(',', current($mine));
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$departure_fields = [];
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foreach ($columns as $row => $column) {
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if (strpos($column, 'departure') === 0) {
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$departure_fields[] = $mine[$row];
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}
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}
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echo array_product($departure_fields); |