65 lines
1.7 KiB
PHP
65 lines
1.7 KiB
PHP
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<?php
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$input_file = '../inputs/day7.txt';
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if (file_exists($input_file)) {
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$input = file_get_contents($input_file);
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if ($input != null) {
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$bag_rules = explode("\n", $input);
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print 'Part 1 answer: ' . solve_part_one($bag_rules) . "\n";
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print 'Part 2 answer: ' . solve_part_two($bag_rules) . "\n";
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}
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}
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function solve_part_one(array $bag_rules): int
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{
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return count(get_parent_colors(parse_bag_rules($bag_rules), 'shiny gold'));
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}
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function solve_part_two(array $bag_rules): int
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{
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return get_content_count(parse_bag_rules($bag_rules), 'shiny gold') - 1;
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}
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function get_content_count(array $rules, string $color): int
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{
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$ret = 0;
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foreach ($rules[$color] as $content_color => $count)
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$ret += $count * get_content_count($rules, $content_color);
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return $ret + 1;
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}
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function get_parent_colors(array $rules, string $color): array
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{
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$ret = [];
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foreach ($rules as $parent_color => $content)
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if (array_key_exists($color, $content))
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$ret = array_merge($ret, [$parent_color], get_parent_colors($rules, $parent_color));
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return array_unique($ret);
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}
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function parse_bag_rules(array $bag_rules): array
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{
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$ret = [];
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foreach ($bag_rules as $rule) {
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if (preg_match('/^(([a-z ]+) bags?) contain ([0-9a-z, ]+ bags?)+\.$/', trim($rule), $matches)) {
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[,, $color, $content] = $matches;
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if ($content === 'no other bags')
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$ret[$color] = [];
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elseif (preg_match_all('/((\d+) ([a-z ]+) bags?)+?,?/', trim($content), $content_matches, PREG_SET_ORDER)) {
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$parsed_content = [];
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foreach ($content_matches as $content_match) {
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[,, $content_qty, $content_color] = $content_match;
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$parsed_content[$content_color] = $content_qty;
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}
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$ret[$color] = $parsed_content;
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}
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}
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}
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return $ret;
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}
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