아일러브커피-원하는 만큼의 원두 사용을 위해 판매해야 하는 메뉴 조합은?

coffee_sale.rb

class Bean
  MENUS = [25, 50, 99, 210, 310, 170, 270, 590, 430, 620, 360, 450, 
    420, 320, 677, 308, 210, 536, 364, 466, 675, 572, 820, 959, 861, 
    1060, 1200, 260, 483].sort
 
  attr_accessor :remain, :menus
 
  def initialize(num)
    if num.is_a?(Bean)
      @remain = num.remain
      @menus = num.menus.clone
    else
      @remain = num
      @menus = []
    end
  end
 
  def subtractable?(num)
    remain >= MENUS[0] && remain - num >= 0
  end
 
  def subtract(num)
    unless subtractable?(num)
      raise ArgumentError.new("Can't subtract #{num} from #{@remain}")
    end
    @remain = @remain - num
    @menus << num
 
    true
  end
 
  def complete?
    @remain == 0 && @menus.length > 0
  end
 
  def to_s
    "<#{@remain}, #{@menus}>"
  end
 
  def self.sell(num)
    Bean::MENUS.reverse_each do |menu|
      new_num = Bean.new(num)
      if new_num.subtractable?(menu)
        new_num.subtract(menu)
        if new_num.complete?
          puts "COMPLETE: " + new_num.to_s
          return true
        else
          return true if sell(new_num)
        end
      end
    end

    false
  end
 
end
 
# 사용해야 하는 원두가 2518 이라면 
Bean.sell(Bean.new(2518))

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