Try Monty Hall problem a lot of times

monty_hall.rb

def doit(change:, doors: [1, 2, 3])
  jackpot = doors.sample
  chosen = doors.sample
  rest = (doors - [chosen])
  drop = (rest - [jackpot]).first

  finally_chosen =
    if change
      (rest - [drop]).first
    else
      chosen
    end

  finally_chosen == jackpot
end

n = 1_000_000

win_change = (n.times.count { doit(change: true) }).to_f / n
win_nochange = (n.times.count { doit(change: false) }).to_f / n

p win_change # 0.665929
p win_nochange # 0.332476
p win_change + win_nochange # 0.998405