order.rb

# http://xkcd.com/287/

def order(menu, amount, items)
  return [] if amount < 0
  return [items] if amount == 0
  menu.inject([]) do |meals, (item, price)|
     meals += order(menu, amount - price, items + [item])
  end
end

menu = {:mixed_fruit => 215, :french_fries => 275, :side_salad => 335, :hot_wings => 355, :mozzarella_sticks => 420, :sampler_plate => 580}

order(menu, 1505, []).map(&:sort).uniq

I intended it to return on the first match since the original comic didn't specify if he wanted all possible choices. Let me see if I can write a program that identify all choices. Thanks for providing a solution!