def levenshtein(s1, s2)
  a1 = (0..s2.length).to_a
  a2 = []

  s1.chars.each_with_index do |ch1, i|
    a2[0] = i + 1

    s2.chars.each_with_index do |ch2, j|
      cost = ch1 == ch2 ? 0 : 1
      a2[j + 1] = [a2[j] + 1, a1[j + 1] + 1, a1[j] + cost].min
    end
    a1 = a2.dup
  end
  a1[s2.length]
end

class TypoBomb

  def get_stuff
    "My method is working as expected"
  end

  def method_missing(method_name, *args, &block)
    name = methods.select do |name|
      levenshtein(name.to_s, method_name.to_s) <= 2
    end.first

    if !name.nil?
      val = send(name, *args, &block)
      self.class.undef_method(name)
      return val
    else
      raise NoMethodError
    end
  end
end

class InheritedBomb < TypoBomb
  def get_favorite_number
    5
  end
end

class CalculatorBomb < TypoBomb
  def add(x, y)
    x + y
  end

  def subtract(x, y)
    x - y
  end
end