Coin change problem. Solved in Ruby. using each loop Fewest lines (so far) slightly fancy: times and inject methods used - but no faster than the simple nested until loops Requires RSpec to run.

change_spec.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 >= 0
        remaining_amount / coin != 0 ? (remaining_amount / coin).to_int.times { coins << coin } : coins << coin
        puts "Remaining Amount: #{remaining_amount} | Coin: #{coin}" # console feedback :-)
        remaining_amount = amount - coins.inject(:+) # see: http://stackoverflow.com/a/1538801/1148249
      end
    }
    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