Day 22 Warmup

palindromes.rb

class Palindromes


  def initialize(hash = {})
    hash[:max_factor] ||= 2
    hash[:min_factor] ||= 1
    @max_factor = hash[:max_factor]
    @min_factor = hash[:min_factor]
    @palins = []
  end


  def is_palindrome?(number)
    number.to_s == number.to_s.reverse
  end


  def generate
    (@min_factor..@max_factor).each do |i|
      (i..@max_factor).each do |j|

        product = i * j
        if is_palindrome?(product)
          palin = PalinNum.find_or_create(product)
          palin.add_factor( [i, j] )
          @palins << palin if [email protected]?(palin)
        end

      end
    end

    @palins.sort!{|p1, p2| p1.value <=> p2.value}
    # p @palins.collect{|palin| palin.value}
  end


  def largest
    @palins[-1]
  end


  def smallest
    @palins[0]
  end


end



class PalinNum

  attr_accessor :pal, :factors

  def initialize(pal = nil)
    # @id = self.class.count + 1
    self.class.all << self
    @pal = pal
  end

  # Findable

  def self.find(pal)
    all.detect{|a| a.pal == pal}
  end

  def self.find_or_create(pal)
    self.find(pal) || self.new(pal)
  end

  # Memorable

  def self.all
    @all ||= []
  end

  # Local Methods

  def value
    @pal
  end

  def add_factor(pair)
    @factors ||= []
    @factors << pair if [email protected]?(pair)
  end

end



# pal = Palindromes.new

# puts pal.is_palindrome?(324923)
# puts pal.is_palindrome?(324423)
# puts pal.is_palindrome?(32423)
# puts pal.is_palindrome?(324922343)

test.rb

require 'fis/test'
require_relative 'palindromes'

include Fis::Test
 
  test 'largest_palindrome_from_single_digit_factors: max 9' do
    palindromes = Palindromes.new(max_factor: 9)
    palindromes.generate
    largest = palindromes.largest
    assert_equal 9, largest.value
    assert [[[3, 3], [1, 9]], [[1, 9], [3, 3]]].include? largest.factors
  end
 
  test 'largest_palindrome_from_double_digit_factors: 10-99' do
    palindromes = Palindromes.new(max_factor: 99, min_factor: 10)
    palindromes.generate
    largest = palindromes.largest
    assert_equal 9009, largest.value
    assert_equal [[91, 99]], largest.factors
  end
 
  test 'smallest_palindrome_from_double_digit_factors: 10-99' do
    palindromes = Palindromes.new(max_factor: 99, min_factor: 10)
    palindromes.generate
    smallest = palindromes.smallest
    assert_equal 121, smallest.value
    assert_equal [[11, 11]], smallest.factors
  end
 
  test 'largest_palindrome_from_triple_digit_factors: 100-999' do
    palindromes = Palindromes.new(max_factor: 999, min_factor: 100)
    palindromes.generate
    largest = palindromes.largest
    assert_equal 906609, largest.value
    assert_equal [[913, 993]], largest.factors
  end
 
  test 'smallest_palindrome_from_triple_digit_factors: 100-999' do
    palindromes = Palindromes.new(max_factor: 999, min_factor: 100)
    palindromes.generate
    smallest = palindromes.smallest
    assert_equal 10201, smallest.value
    assert_equal [[101, 101]], smallest.factors
  end