compose-cycles.clj

(defn compose-cycles [cycle-a cycle-b]
  (let [inv-cycle-a (clojure.set/map-invert cycle-a)]
    (reduce-kv
      (fn [acc k v]
        (cond
          (contains? inv-cycle-a k) (assoc acc (get inv-cycle-a k) v)
          (contains? cycle-a k) acc
          :else (assoc acc k v)))
      cycle-a
      cycle-b)))  

(defn compose-cycles [cycle-a cycle-b]
  (merge
    cycle-b
    (into {}
      (for [[k v] cycle-a]
        [k (get cycle-b v v)]))))