WJ's homework.

spec.rb

require './string'

describe "String#condensify" do
  it "encodes a string" do
    input  = "AAASSSDDDDRDDSASSDDDSSSAD"
    output = "3A3S4DR2DSA2S3D3SAD"
    input.condensify.should == output
  end

  it "encodes a string with no repeats" do
    input = "ABCDEFG"
    input.condensify.should == input
  end
end

string.rb

class String
  def condensify
    split_by_repeating.map! do |item|
      if item.length > 1
        "#{item.length}#{item[0]}"
      else
        item
      end
    end.join
  end

  def split_by_repeating
    hero = []
    self.each_char do |char|
      if hero.last && hero.last[0] == char
        hero[hero.length-1] = hero.last + char
      else
        hero << char
      end
    end
    hero
  end
end