Created
February 22, 2015 06:58
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Monty Hall Problem Simulator
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number_of_doors = 3 | |
monty_is_random = false | |
switch_choice = true | |
number_of_simulations = 10000 | |
# number_of_correct_initial_guesses = 0 | |
number_of_times_monty_accidentally_exposes_car = 0 | |
number_of_wins = 0 | |
doors = (1..number_of_doors).inject({}){|h,i| h[i] = nil; h } | |
# => {1=>nil, 2=>nil, 3=>nil} | |
door_with_car_behind_it = rand(number_of_doors) + 1 | |
doors[door_with_car_behind_it] = "CAR" | |
doors.keys.each{|door_number| doors[door_number] ||= "Camel" } | |
# => (eg.) {1=>"CAR", 2=>"Camel", 3=>"Camel"} | |
number_of_simulations.times do | |
first_guess = rand(number_of_doors) + 1 | |
montys_remaining_choices = doors.keys - [first_guess] | |
if monty_is_random | |
exposed = false | |
while montys_remaining_choices.size > 1 && !exposed | |
montys_door = montys_remaining_choices[rand(montys_remaining_choices.size)] | |
if doors[montys_door] == "CAR" | |
number_of_times_monty_accidentally_exposes_car += 1 | |
exposed = true | |
else | |
montys_remaining_choices -= [montys_door] | |
end | |
end | |
next if exposed | |
else | |
if doors[first_guess] == "CAR" | |
# Just choose any of the remaining doors to keep closed, might as well be the first | |
montys_remaining_choices = montys_remaining_choices[0..0] | |
else | |
# Keep the CAR door closed | |
montys_remaining_choices = [door_with_car_behind_it] | |
end | |
end | |
raise "Oops" unless montys_remaining_choices.size == 1 | |
if switch_choice | |
new_guess = montys_remaining_choices[0] | |
else | |
new_guess = first_guess | |
end | |
if doors[new_guess] == "CAR" | |
number_of_wins += 1 | |
end | |
end | |
percent_of_all = (number_of_wins.to_f / number_of_simulations)*100 | |
percent_of_valid = (number_of_wins.to_f / (number_of_simulations - number_of_times_monty_accidentally_exposes_car))*100 | |
puts "Player won #{number_of_wins} times or #{percent_of_all.round(1)}% of all simulations.\n" + | |
"Monty accidentally exposed the car #{number_of_times_monty_accidentally_exposes_car} times.\n" + | |
"Therefore player won #{percent_of_valid.round(1)}% of valid simulations" |
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