wiki_path

gistfile1.rb

require 'nokogumbo'
require 'uri'

def print_parents visited, path
	parent = path
	while parent = visited[parent]
		puts "parent: %s" % URI.unescape(parent)
	end
end

def find_links url
	puts URI.unescape(url)

	doc = Nokogiri::HTML5.get(url)
	links = doc.css('a')
	links
		.map { |link| link['href'] }
		.compact
		.select { |h| h.start_with? '/wiki/' }
		.reject { |h| h.include? ':' or h.include? '#'}
end

def search_path from_term, to_term, lang
	queue = []
	visited = {}

	from_path = URI.escape("/wiki/#{from_term}")
	to_path = URI.escape("/wiki/#{to_term}")

	visited[from_path] = nil

	queue << from_path

	while queue.any?
		path = queue.shift
		new_paths = find_links get_url(path, lang)

		new_paths.each do |p|
			unless visited.has_key? p
				visited[p] = path
				queue << p
			end

			if p == to_path
				puts "\n>> Found: #{URI.unescape(p)}"
				print_parents visited, p
				return
			end
		end
	end

	puts "not found"
end

def get_url path, lang
	"https://%s.wikipedia.org%s" % [lang, path]
end

search_path('Sort', 'SAP', 'ru')

На Crystal еще быстрее будет, наверное (пришел отсюда http://habrahabr.ru/post/260883/#comment_8472729)