31 lines
818 B
PHP
31 lines
818 B
PHP
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<?php
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[$template, $rules] = explode("\n\n", file_get_contents('./input.txt'));
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$template = str_split($template);
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$pair_insertion_rules = [];
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foreach (explode("\n", $rules) as $rule) {
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[$key, $value] = explode(' -> ', $rule);
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$pair_insertion_rules[$key] = $value;
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}
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for ($i = 0; $i < 40; $i++) {
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$tmp = [];
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foreach ($template as $i_char => $char) {
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if (array_key_exists($i_char+1, $template)) {
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$tmp[] = $char;
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$pair = $char . $template[$i_char + 1];
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if (array_key_exists($pair, $pair_insertion_rules)) {
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$tmp[] = $pair_insertion_rules[$pair];
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}
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}
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}
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$tmp[] = array_pop($template);
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$template = $tmp;
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echo $i."\n";
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}
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$count_char = array_count_values($template);
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echo max($count_char) - min($count_char);
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