JavaOne Talk: Ruby Reversible Numbers

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class RubyReversible
  def initialize(max)
    @max = max
    @numReversible = nil
  end

  def allOdd(n)
    digits = n.to_s.split(//)
    digits.length == digits.map{|c| c.to_i}.select{|i| 
        i % 2 == 1}.length
  end

  def reverse(n)
    n + n.to_s.reverse.to_i
  end

  def reversible(n)
    allOdd(reverse(n))
  end

  def countReversible()
    @numReversible ||= (11..@max).select{|i| 
        reversible(i)}.length
    @numReversible 
  end
end