抵抗の合計を求める

kairo.rb

class Circuit
  def initialize(circuit)
    @circuit = analyze(circuit)
  end

  def calc
    @circuit.inject(0) {|memo, item| memo + item.val}.truncate
  end

  def analyze(circuit)
    circuit.map { |resistance| Resistance.new(resistance) }
  end
end

class Resistance
  attr_accessor :str, :val

  def self.set_hash(resistances)
    @@hash = resistances
  end

  def initialize(str)
    @str = str
    @val = set_val
  end

  def set_val
    return @@hash[str] if series?

    1 / (str.split('').map {|a| 1 / @@hash[a] }.inject(:+))
  end

  def series?
    @str.length == 1
  end

  def parallel?
    !series?
  end
end

class InputParser
  def initialize(input_file)
    @lines = input_file.readlines.map { |line| line.split(' ') }
  end

  def parse
    n = @lines[0].first.to_i

    resistances = @lines[1..n].each_with_object({}) { |(type, resistance), result|
      result[type] = resistance.to_f
    }

    circuit = @lines[n + 1]

    return resistances, circuit
  end
end

resistances, circuit = InputParser.new(ARGF).parse

Resistance.set_hash(resistances)
p Circuit.new(circuit).calc