birthday.rb

MY_BIRTHDAY = 89
SIMULATIONS = 100000

# true if found someone with my birthday
def run_test(num_people)
  ((1..num_people).filter do
    rand(365) == MY_BIRTHDAY
  end).length > 0
end

# ratio between true/falses on the func above
def simulate_n_times(num_people)
  puts "Simulating for #{num_people}"
  true_false_array = (1..SIMULATIONS).map do
    run_test(num_people)
  end

  answer = true_false_array.filter { |item| item }.length / SIMULATIONS.to_f

  puts "Answer is ~ #{answer*100}%"
end

simulate_n_times(182)
simulate_n_times(183)
simulate_n_times(253)