(def max-path-length 10)

(defn get-paths
  ([current end] (get-paths current end [] 0))
  ([current end path depth]
     (if (= current end)
       (concat path [current])
       (let [neighbours (filter #(not (lazy-contains? (flatten path) %1))
                                (get-neighbours current))]
         (if (or (= (count neighbours) 0)
                 (>= depth max-path-length))
           (concat path [nil])
           (map (fn [item]
                  (get-paths item end (concat path [current]) (+ depth 1)))
                neighbours))))))

(defn get-shortest-path [start end]
  (apply min-key count
         (filter #(and (seq? %1) (= (last %1) end))
                 (tree-seq seq? seq (get-paths start end)))))