http://math.stackexchange.com/a/2000952/86776

cookies.rb

# http://math.stackexchange.com/q/2000829/86776

require 'set'

class Jar
  @cookies

  def initialize
    @cookies = Set.new
    (1..10).each do |k|
      @cookies.add(k)
    end
  end

  def to_s
    a = @cookies.to_a
    s = '{ ' + a.join(', ') + ' }'
  end

  def eat
    @cookies.each do |cookie|
      r = rand(2)
      if r == 1
        @cookies.delete(cookie)
      end
    end
  end

  def empty?
    @cookies.empty?
  end
end

  
def run
  jar = Jar.new
  d = 0
  begin
    jar.eat
    d += 1
    #puts "d: #{d} jar: #{jar}"
  end while not jar.empty?
  d
end

def sim
  n = 1_000_000
  s = 0
  n.times do |k|
    d = run
    s += d
  end
  avg = s * 1.0 / n
  puts "n = #{n}, avg = #{avg}"
end

sim