Coin Change Problem Solved in 5 Lines of Ruby. ( Method code on SINGLE Line! ;-) Do NOT do this in RL kids! ( Seriously Unreadable/Unmaintainable! Simply a Thought Exercise in taking compression to its logical conclusions ... ) Surprisingly fast to execute! :-P

change_rspec.rb

class Change
  def change(amount)
    available_coins, coins, remaining_amount = [100,50,25,10,5,1], [], amount; available_coins.each { |coin| if ((remaining_amount/coin).to_int > 0) then (remaining_amount/coin).to_int.times { coins << coin }; remaining_amount = amount-coins.inject(:+) end }; return coins
  end
end

describe Change do
  it "returns [1] for 1" do
    expect(subject.change(1)).to eq [1]
  end

  it "returns [1, 1, 1, 1] for 4" do
    expect(subject.change(4)).to eq [1,1,1,1]
  end

  it "returns [5, 1] for 6" do
    expect(subject.change(6)).to eq [5,1]
  end

  it "returns [25, 10, 10, 1, 1, 1] for 48" do
    expect(subject.change(48)).to eq [25,10,10,1,1,1]
  end

  it "returns [100, 25, 10, 5, 1, 1] for 142" do
    expect(subject.change(142)).to eq [100,25,10,5,1,1]
  end

  it "returns [100,100,50,25,10,1] for 286" do
    expect(subject.change(286)).to eq [100,100,50,25,10,1]
  end
end