Weekly Challenge - Pythagorean Triplet

pythagorean_triplet.rb

# A class for auto-generating pythagorean triplets according to
# certain criteria, as well as testing whether a set of 3 numbers
# is a valid pythagorean triplet.
class Triplet
  def initialize(*nums)
    @nums = nums
  end

  def sum
    @nums.reduce(:+)
  end

  def product
    @nums.reduce(:*)
  end

  def pythagorean?
    @nums[0]**2 + @nums[1]**2 == @nums[2]**2
  end

  class << self
    def where(options)
      min = options[:min_factor] || 1
      max = options[:max_factor]
      sum = options[:sum]
      factors = (min..max).to_a

      factors.combination(3).map do |a, b, c|
        triplet = Triplet.new(a, b, c)
        triplet if valid?(triplet, sum)
      end.compact
    end

    private

    def valid?(triplet, expected_sum)
      if expected_sum
        triplet.pythagorean? && triplet.sum == expected_sum
      else
        triplet.pythagorean?
      end
    end
  end
end