Rework on uni year one assignment question. Given any amount in cents, calculate changes

gistfile1.rb

module ChangeMachine

  class IdiotEncountered < StandardError; end

  AVAILABLE_UNITS = [10000, 5000, 2000, 1000, 500, 200, 100, 50, 20, 10, 5]

  def self.show_me_the_money(dollar_in_cents)
    raise IdiotEncountered, "You are an idiot, no such amount in AUS..." unless dollar_in_cents % 5 == 0

    dispense(dollar_in_cents)
  end

  def self.dispense(dollar_in_cents)
    return {} if dollar_in_cents == 0

    unit = AVAILABLE_UNITS.select{|u| u <= dollar_in_cents}.max

    {unit => (dollar_in_cents / unit)}.merge(dispense(dollar_in_cents % unit))
  end
end

puts ChangeMachine.show_me_the_money(37500).inspect

I like your original version better :P

@tommyli that's the exact version I submitted ... Now thinking about it, tutoring is hard work. It's like a torture EVERY single time you mark a year one student assignment... well most of them anyway