https://github.com/Hexlet/battle_asserts/pull/106

remove_duplicates.clj

; remove duplicates from sequence
; third
(defn compress [seq]
  (->> seq
    (reduce #(cond
                (= %2 (first %1)) %1
                :else (conj %1 %2))
            nil)
    (reverse)))
  
; vs second
(defn compress [seq]
  (loop [head [] tail seq]
    (cond
      (nil? tail) nil
      (nil? (second tail)) (concat head tail)
      (= (first tail)
         (first (rest tail))) (recur head (rest tail))
      :else (recur (conj head
                         (first tail))
                   (rest tail)))))
; vs first
(defn compress_ [seq]
  (cond
    (nil? seq) nil
    (nil? (second seq)) seq
    (= (first seq)
       (first (rest seq))) (compress_ (rest seq))
    :else (cons (first seq)
                (compress_ (rest seq)))))