ktc.clj

(defn veckey-to-set [veckey]
  (reduce (fn [[column set-key] k]
            (if (contains? set-key k)
              [column set-key]
              [(conj column k) (conj set-key k)]))
          [[] #{}]
          veckey))

(defn handle-rest-char [set-key]
  (let [char-seq (map char (range (int \A) (inc (int \Z))))]
    (reduce #(if (contains? set-key %2) %1 (conj %1 %2)) [] char-seq)))

(defn take-every-n [start n coll]
  (let [length (dec (count coll))]
    (loop [idx start
           result []
           ]
      (cond
        (<= idx length) (recur (+ idx n) (conj result (get coll idx)))
        :else result))))

(defn trasform-key [key]
  (let [vec-key (into [] key)
        [first-column set-key] (veckey-to-set vec-key)
        rest-chars (handle-rest-char set-key)
        sorted-key (sort-by second (map-indexed vector first-column))
        ]
                                        ;[first-column set-key rest-chars sorted-key]
    (take-every-n 0 5 rest-chars)
    )
  )

(trasform-key "SECRET")