Find the largest palindrome (of number_of_digits length) that is also a perfect square. E.g., largest_pal_perf_sq(15) returns 900_075_181_570_009

largestPalPerfSq.rb

def palindrome?(text)
  return true if text.length <= 1
  return false if text[0] != text[text.length - 1]
  return palindrome?(text[1..-2])
end


def prepare_range(number_of_digits)
  big = ''
  sml = '1'

  number_of_digits.times do
    big << '9'
    sml << '0'
  end

  # Remove extra zero
  sml.chop!

  return [sml, big]
end


def largest_pal_perf_sq(number_of_digits)
  range = prepare_range(number_of_digits)

  lower_range = Math.sqrt(range[0].to_i).ceil
  upper_range = Math.sqrt(range[1].to_i).floor

  upper_range.downto(lower_range) do |sqrt|
    number_in_question = sqrt * sqrt
    return number_in_question if palindrome?(number_in_question.to_s)
  end

  return false
end