compressor

compressor.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  gem 'minitest'
end

require 'minitest/autorun'

class Compressor
	def self.compress!(array)
    zero_or_one_index = array.rindex { |element| [0,1].include? element }
    array.slice!(0, zero_or_one_index) if zero_or_one_index
    deleting = true
    while deleting
      deleting = false
      array.each_with_index do |element, index|
        next if index.zero?
        previous_element = array[index - 1]
        if (previous_element == 0 && element.even?) || 
           (previous_element == 1 && element.odd?)
          array.delete_at(index)
          deleting = true
          break
        end
      end
    end
    array.shift if array[0] == 1
  end
end

class CompressorTest < Minitest::Test
  def test_simple
    array = [1, 0]
    Compressor.compress!(array)
    assert_equal([0], array)
  end

  def test_removes_previous_numbers
    array = [3, 2, 0]
    Compressor.compress!(array)
    assert_equal([0], array)
  end

  def test_removes_adjacent_positive_numbers
    array = [2, 0, 4, 6, 7]
    Compressor.compress!(array)
    assert_equal([0, 7], array)
  end

  def test_removes_adjacent_negative_numbers
    array = [2, 0, 4, 1, 3, 6]
    Compressor.compress!(array)
    assert_equal([6], array)
  end

  def test_long_array
    array = [3, 2, 0, 4, 1, 3, 6, 8, 5]
    Compressor.compress!(array)
    assert_equal([6, 8, 5], array)
  end
end