grid_gen.rb

class Grid
  class << self
    alias :rand :new
  end

  def initialize(width, height)
    @w, @h = width, height
    
    @answer = (0..@h).inject([]) do |ary, x|
      ary << (0..@w).inject([]) do |sub_ary, y|
        sub_ary << (rand(2) == 1)
      end
    end

    @grid = (0...@h).inject([]) do |ary, x|
      ary << (0...@w).inject([]) do |sub_ary, y|
        sub_ary << @answer[x, 2].inject(0) do |sum, sub_answer|
          sum + sub_answer[y, 2].select { |i| i }.size
        end
      end
    end
  end

  def print_on(io)
    @grid.each { |line| io.puts line * " " }
  end

  def [](x, y)
    @grid[x][y]
  end

  attr_reader :w, :h, :answer
end

Grid.new(5, 5).print_on $stdout