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require 'set'
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# input = DATA.read
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input = File.read('11.input')
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paths = {}
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ipaths = {}
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known_terminators = Set.new
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input.strip.lines.each do |line|
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from, to = line.strip.split(": ")
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from = from.intern
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to = to.split(" ").map(&:intern)
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paths[from] = to
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to.each do |t|
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ipaths[t] ||= []
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ipaths[t] << from
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end
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end
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$count = 0
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def traverse(paths, spot, seen_dac, seen_fft)
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$count += 1
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paths[spot].each do |next_spot|
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if next_spot == :out
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$count += 1 if seen_dac && seen_fft
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else
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traverse(paths, next_spot, seen_dac || next_spot == :dac, seen_fft || next_spot == :fft)
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end
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end
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$count -= 1
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end
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traverse(paths, :svr, false, false)
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p $count
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__END__
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svr: aaa bbb
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aaa: fft
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fft: ccc
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bbb: tty
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tty: ccc
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ccc: ddd eee
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ddd: hub
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hub: fff
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eee: dac
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dac: fff
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fff: ggg hhh
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ggg: out
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hhh: out
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