8-puzzle

gistfile1.clj

(ns playground.eightpuz)

(defn correct [b] (= b [1 2 3 8 0 4 7 6 5]))
(def dirs {'l -1 'r 1 'u -3 'd 3})

(defn move [b dir]
  (let [idx (.indexOf b 0)
        col (mod idx 3)
        tgt (+ idx (dirs dir))]
    (if
      (or (and (= 'l dir) (= 0 col))
          (and (= 'r dir) (= 2 col))
          (and (= 'u dir) (> 3 idx))
          (and (= 'd dir) (< 5 idx)))
      nil
      (assoc (assoc b idx (b tgt)) tgt 0))))

(defn solve [boardstack moves]
  (let [cur (first boardstack)]
    (cond (correct cur) moves
          (some #{cur} (rest boardstack)) nil
          :else (first (filter identity (map #(solve (cons boardstack (move cur %)) (conj moves %))
                     (keys dirs)))))))
(keys dirs)

(correct (move [1 2 3 0 8 4 7 6 5] 'r))
;(solve (list [1 2 3 0 8 4 7 6 5]) [])