Webpage counting interview question

webpage_counting_solution.rb

require 'set'

Page = Struct.new(:url) do
  LINK_TABLE = {
    "google.com" => %w[google.com/maps google.com/mail],
    "google.com/mail" => %w[google.com google.com/mail/drafts google.com/mail/spam],
    "google.com/mail/drafts" => %w[google.com google.com/mail google.com/mail/spam],
    "google.com/mail/spam" => %w[google.com google.com/mail google.com/mail/drafts],
    "google.com/maps" => %w[google.com google.com/my-maps google.com/mail],
    "google.com/my-maps" => %w[google.com google.com/maps]
  }

  def links
    LINK_TABLE.fetch(url)
  rescue KeyError
    puts "unknown url: #{url}"
  end
end

def count_pages(starting_url)
  visited_urls = Set.new
  urls_to_visit = [starting_url]

  until urls_to_visit.empty?
    current_page = Page.new(urls_to_visit.pop)
    visited_urls.add(current_page.url)

    current_page.links.each do |link|
      unless visited_urls.include?(link)
        urls_to_visit.push(link)
      end
    end
  end

  visited_urls.size
end

puts count_pages("google.com")