52 lines
1.4 KiB
PHP
52 lines
1.4 KiB
PHP
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<?php
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$reports = array_filter(explode("\n", file_get_contents(__DIR__.'/input.txt')), static fn($line) =>!empty($line));
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$number_of_safe_reports = 0;
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function is_report_safe(string $report)
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{
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$levels = explode(' ', $report);
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$current_number = null;
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$current_way = null;
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foreach ($levels as $level) {
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if ($current_number === null) {
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$current_number = $level;
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} else {
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if ($current_number === $level) {
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return false;
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}
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if ($current_number > $level) {
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if ($current_number - $level > 3) {
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return false;
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}
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if ($current_way === null) {
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$current_way = 'd';
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} elseif ($current_way !== 'd') {
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return false;
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}
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}
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if ($current_number < $level) {
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if ($level - $current_number > 3) {
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return false;
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}
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if ($current_way === null) {
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$current_way = 'a';
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} elseif ($current_way !== 'a') {
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return false;
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}
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}
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$current_number = $level;
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}
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}
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return true;
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}
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foreach ($reports as $report) {
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if (is_report_safe($report)) {
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$number_of_safe_reports++;
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}
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}
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echo sprintf('Number of safe reports : %u', $number_of_safe_reports);
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exit;
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