39 lines
755 B
Ruby
39 lines
755 B
Ruby
# frozen_string_literal: true
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input = File.read('./input').split("\n\n").map { |r| r.split("\n") }
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$mem = {}
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$lines = input[1]
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$rules = input.first.map do |i|
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k, v = i.match(/(\d+): (.*)/).captures
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[k, v.split('|').map do |x|
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x.split(' ').reject(&:empty?).compact.map do |y|
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y.gsub('"', '')
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end
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end]
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end.sort_by(&:first).to_h
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def rules(key)
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$mem[key] ||= begin
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either_or = $rules[key]
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return key unless either_or
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pair = either_or.map do |group|
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group.map do |sub_rule|
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rules(sub_rule)
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end.join('')
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end.join('|')
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if pair.include?('|')
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'(' + pair + ')'
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else
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pair
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end
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end
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end
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re = Regexp.new('^' + rules('0') + '$')
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puts $lines.select { |line| re.match(line) }.size
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