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Task/Best-shuffle/Clojure/best-shuffle.clj

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+(defn score [before after]
+   (->> (map = before after)
+	(filter true? ,)
+	count))
+
+(defn merge-vecs [init vecs]
+  (reduce (fn [counts [index x]]
+		 (assoc counts x (conj (get counts x []) index)))
+	  init vecs))
+
+(defn frequency
+  "Returns a collection of indecies of distinct items"
+  [coll]
+  (->> (map-indexed vector coll)
+       (merge-vecs {} ,)))
+
+(defn group-indecies [s]
+  (->> (frequency s)
+       vals
+       (sort-by count ,)
+       reverse))
+
+(defn cycles [coll]
+  (let [n (count (first coll))
+	cycle (cycle (range n))
+	coll (apply concat coll)]
+    (->> (map vector coll cycle)
+	 (merge-vecs [] ,))))
+
+(defn rotate [n coll]
+  (let [c (count coll)
+	n (rem (+ c n) c)]
+    (concat (drop n coll) (take n coll))))
+
+(defn best-shuffle [s]
+  (let [ref (cycles (group-indecies s))
+	prm (apply concat (map (partial rotate 1) ref))
+	ref (apply concat ref)]
+    (->> (map vector ref prm)
+	 (sort-by first ,)
+	 (map second ,)
+	 (map (partial get s) ,)
+	 (apply str ,)
+	 (#(vector s % (score s %))))))
+
+user> (->> ["abracadabra" "seesaw" "elk" "grrrrrr" "up" "a"]
+	   (map best-shuffle ,)
+	   vec)
+[["abracadabra" "bdabararaac" 0]
+ ["seesaw" "eawess" 0]
+ ["elk" "lke" 0]
+ ["grrrrrr" "rgrrrrr" 5]
+ ["up" "pu" 0]
+ ["a" "a" 1]]