RO・サマスペ2012の宿題シミュレーション

homework.rb

# coding: utf-8

# n=5で50%のつもり
def hit?(n)
  rand(10) <= (n-1) ? true : false
end

# パターン1：かぶりなし＝10回成功したら終わり
def pattern1(r)
  count = 0
  hit = 0
  loop do
    break if hit >= 10
    count += 1
    next unless hit?(r)
    hit += 1
  end
  count
end

# パターン2：かぶりあり
def pattern2(r)
  count = 0
  items = []
  loop do
    break if items.size >= 10
    count += 1
    next unless hit?(r)
    i = rand(10) # 0-9まで出る
    items << i unless items.include?(i)
  end
  count
end

# main
hit_ratio = ARGV[0].to_i
exec_count = ARGV[1].to_i

r1 = 0
r2 = 0
exec_count.times do
  r1 += pattern1(hit_ratio)
  r2 += pattern2(hit_ratio)
end

puts "pattern1 : #{(r1.to_f/exec_count.to_f).round(2)}"
puts "pattern2 : #{(r2.to_f/exec_count.to_f).round(2)}"

結果：
ruby homework.rb 5 100000
pattern1 : 20.01
pattern2 : 58.63