(defn find-open-position [puzzle]
  (cond (nil? (puzzle [1 1])) [1 1]
        :else nil))

(defn find-free-number [puzzle position]
  (cond (nil? position) nil
        :else 1))

(defn find-next-move [puzzle]
 (let [open-position (find-open-position puzzle) free-number (find-free-number puzzle open-position)]
   (cond (nil? free-number) nil
         :else {:position open-position
                :number free-number})))

(defn solve [puzzle]
  (let [next-move (find-next-move puzzle)]
    (cond (nil? next-move) puzzle
          :else (solve (assoc puzzle (next-move :position) (next-move :number))))))

;;
(clojure.pprint/pprint (solve {[0 0] 1}))