Problem: Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to swi…

month_hall_problem.rb

def createDoors
    doors = [false, false, false]
    # set one door equal to the car
    doors[rand(3)] = true
    doors
end
 
def openADoorThatHasAGoat(doors, userChoice)
    # return the first false element after removing the users choice and a true value (if present)
    ([0, 1, 2] - [userChoice, doors.index(true)]).first
end
 
def changeUserChoice(choices)
    # return the door remaining after removing the users original choice and the goat
    ([0, 1, 2] - choices).first
end
 
def play(switch_decision)
    # create the doors and make 1 door == true
    doors = createDoors()
    # contestant picks their door
    userChoice1 = rand(3)
    # host removes a goat
    hostChoice = openADoorThatHasAGoat(doors, userChoice1)
    if switch_decision == "switch"   
      userChoice2 = changeUserChoice([userChoice1, hostChoice])
      # retun true if the index of the switch matches the index of true in doors
      doors.index(true) == userChoice2
    elsif switch_decision == "dont switch"   
       doors.index(true) == userChoice1
    end
end

 
# games = 10000
# wins = 0
# games.times { wins += 1 if play("switch") }
# p ("#{100*wins/games}% win rate")