The ultimate searching winning position tic-tac-toe algo.

tic-tac-toe.clj

;; Playing with conciness and expressivity in Clojure.
;; Not an exercise in efficiency, there are better solutions.
;; It works for different NxN sizes and it's lazy, stopping 
;; at the first winning combination for the given player.

(defn winner? [player game]
  (let [size (count game)
        idxs (range size)]
    (->> [[x idx] [idx y] [idx idx] [idx (- (dec size) idx)]]
         (map (fn [[x y]] ((game x) y)))
         (for [x idxs y idxs idx idxs])
         (apply mapcat list)
         (partition size)
         (some #(apply = player %)))))

(winner? :x [[:x  :o  nil] 
             [nil :x  :o] 
             [:o  :x  :x]])
;; true

(winner? :o [[:o  :o :x :x] 
             [:x  :x :o :o] 
             [:o  :x :o :x]
             [:o  :x :o :x]])
;; nil