213.rb

class Rule90
  def initialize input
    @input = input.split(//).map(&:to_i)
  end

  def get_next target_index, input
    input[target_index + 1]
  end

  def get_prev target_index, input
    input[target_index - 1]
  end

  def evolve input
    input.map.with_index do |item, target_index|
      if target_index == 0
        prev_val = 0
        next_val = get_next target_index, input
      elsif target_index == input.length - 1
        next_val = 0
        prev_val = get_prev target_index, input
      else
        next_val = get_next target_index, input
        prev_val = get_prev target_index, input
      end
      prev_val == next_val ? 0 : 1
    end
  end

  def draw_x arr
    row = arr.map do |item|
      if item == 0
        " "
      else
        "x"
      end
    end
    puts row.join("")
  end

  def iterate_and_draw 
    input = @input
    draw_x input 
    24.times do
      input = evolve input
      draw_x input
    end
  end
end

r90 = Rule90.new("00000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000")
r90.iterate_and_draw

Daily programmer solution for cellular automation.