*4clojure-problem-119*.clj

(defn win-tic-tac-toe
  [side b]
  (let [b (->> b
               flatten
               (map-indexed vector))
        check-win (fn
                    [[a b c d e f g h i]]
                    (->> [[a b c] [d e f] [g h i]
                          [a d g] [b e h] [c f i]
                          [a e i] [c e g]]
                         (filter (partial apply =))
                         (map first)
                         (drop-while (partial = :e))
                         first))]
    (->> b
         (filter #(= :e (second %)))
         (map first)
         (filter (comp check-win
                       vals
                       #(assoc (into (sorted-map) b) % side)))
         (map (juxt #(quot % 3) #(mod % 3)))
         (into #{}))))