遊戯王 1枚初動率

run.sh

for i in $(seq 3 12); do ruby yugioh_probability.rb 40 5 $i; done
# deck: 40, hand: 5, hit: 3 -> 33.76%
# deck: 40, hand: 5, hit: 4 -> 42.71%
# deck: 40, hand: 5, hit: 5 -> 50.66%
# deck: 40, hand: 5, hit: 6 -> 57.71%
# deck: 40, hand: 5, hit: 7 -> 63.93%
# deck: 40, hand: 5, hit: 8 -> 69.40%
# deck: 40, hand: 5, hit: 9 -> 74.18%
# deck: 40, hand: 5, hit: 10 -> 78.34%
# deck: 40, hand: 5, hit: 11 -> 81.95%
# deck: 40, hand: 5, hit: 12 -> 85.06%

yugioh_probability.rb

# frozen_string_literal: true

def factorial(number) = Rational((1..number).reduce(1, :*))
def permutation(cards, hand) = factorial(cards) / factorial(cards - hand)
def probability(deck, hand, hit) = 1 - (permutation(deck - hit, hand) / permutation(deck, hand))

def main(deck:, hand:, hit:)
  percent = "#{format('%.2f', probability(deck, hand, hit) * 100)}%"
  puts "deck: #{deck}, hand: #{hand}, hit: #{hit} -> #{percent}"
end

deck = (ARGV[0] || 40).to_i
hand = (ARGV[1] || 5).to_i
hit  = (ARGV[2] || 7).to_i
main(deck:, hand:, hit:) if __FILE__ == $PROGRAM_NAME