200224

Crystal


A320843(2)

Crystal で計算してみた。

class Count
  @@cnt = 0
  def initialize
    @@cnt += 1
  end
  def self.instances
    @@cnt
  end
  def self.to_zero
    @@cnt = 0
  end
end

def search(a, num, n)
  if num == n + 1
    Count.new
  else
    (1..n).each{|i|
      if a[i] == 0
        if num % i == 0 || i % num == 0
          a[i] = num
          search(a, num + 1, n)
          a[i] = 0
        end
      end
    }
  end
end

def a320843(n)
  a = [0] * (n + 1)
  Count.to_zero
  search(a, 1, n)
  Count.instances
end

p (0..20).map{|i| a320843(i)}

出力結果
[1, 1, 2, 3, 8, 10, 36, 41, 132, 250, 700, 750, 4010, 4237, 10680, 24679, 87328, 90478, 435812, 449586, 1939684]