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38 lines
903 B
38 lines
903 B
reactions = ARGF.read.strip.lines.each.with_object({}) {|line, h|
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reactands = line.scan(/(\d+) (\w+)/).map {|q,c| [c,q.to_i] }
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c, q = reactands.pop
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h[c] = { quantity: q, inputs: reactands }
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}.to_h
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Factory = Struct.new(:reactions, :supply, :ores_used) do
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def produce(chemical)
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self.ores_used ||= 0
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case reaction = reactions[chemical]
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in { quantity: quantity, inputs: inputs }
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until inputs.all? {|c,q| supply[c] >= q }
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inputs
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.select {|c,q| supply[c] < q }
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.each do |c,_|
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produce(c)
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end
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end
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inputs.each do |c,q|
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self.ores_used += q if c == "ORE"
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supply[c] -= q
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end
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supply[chemical] += quantity
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else
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fail "unexpected reaction: #{reaction}"
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end
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end
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end
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supply = Hash.new(0)
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supply["ORE"] = Float::INFINITY
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factory = Factory.new(reactions, supply)
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factory.produce("FUEL")
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