Change Kata

change.rb

class Changer

  attr_accessor :change

  def initialize
    @change = []
  end

  def make_change(num)

    changed = [["q", 25],
               ["d", 10],
               ["n",  5],
               ["p",  1]]


    array = build_change_count_array(changed, num)

    build_change_array(array)

  end

  def build_change_count_array(changed, num)
    array = []
    changed.each do |arg|
      array << [num/arg[1], arg[0]]
      num = num % arg[1]
    end
    array
  end

  def build_change_array(array)
    array.each do |coin|
      add_to_change(coin[0], coin[1])
    end
  end

  def add_to_change(repeats, change_character)
    repeats.times { @change << change_character}
  end
end

change_spec.rb

require 'spec_helper'
require_relative '../lib/change'

describe Changer do

  let(:money) {Changer.new}

  it "returns a penny" do
    money.make_change(1)
    money.change.should == %w(p)
  end

  it "returns two pennies" do
    money.make_change(2)
    money.change.should == %w(p p)
  end

  it "returns a nickel" do
    money.make_change(5)
    money.change.should == %w(n)
  end

  it "returns a nickel and a penny" do
    money.make_change(6)
    money.change.should == %w(n p)
  end

  it "returns a dime" do
    money.make_change(10)
    money.change.should == %w(d)
  end

  it "returns a dime, nickel, and two pennies" do
    money.make_change(17)
    money.change.should == %w(d n p p)
  end

  it "returns a quarter" do
    money.make_change(25)
    money.change.should == %w(q)
  end

  it "returns two quarters and a penny" do
    money.make_change(51)
    money.change.should == %w(q q p)
  end

  it "returns a three quarters, two dimes, and four pennies"do
    money.make_change(99)
    money.change.should == %w(q q q d d p p p p)
  end
end

I asked Josh Cheek to critique my implementation. He sat down and made me a personal screencast. What a standup guy! Screencast here:

http://vimeo.com/38729506

followup screencast here, with Josh's roommate, Michael:

http://vimeo.com/38732037

Loved that last screencast -- super simple!