euler3.rb

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-

require 'prime' # 反則

NUMBER = 600851475143
prime_factor = []
Prime.each(NUMBER) do |p|  # おそい
  prime_factor.push p if NUMBER % p == 0
  break if NUMBER < 2 * p
end
puts prime_factor.join(',')