frog.rb

# inspired by Matt Parker's Frog Problem video
# https://www.youtube.com/watch?v=ZLTyX4zL2Fc

module Froggie
  class << self
    def calculate_average_jumps(n_frogs = 10_000, n_spots = 10)
      total_jumps = 0.0
      n_frogs.times { total_jumps += Frog.new(n_spots).jump! }
      total_jumps / n_frogs
    end
  end

  class Frog
    def initialize(n_spots = 10)
      @jumps_taken     = 0
      @remaining_spots = n_spots
    end

    def jump!
      return @jumps_taken if @remaining_spots.zero?
      @jumps_taken     += 1
      @remaining_spots -= (rand(@remaining_spots) + 1)
      jump!
    end
  end
end