Raw method of grouping IP addresses. Desctructive operation.

clojure group ips

(defn group-ips [ips]
  (if (> (count ips) 1)
    (let [ips (->> ips distinct sort-ips)
          to-array (fn [ip-str] (str/split ip-str #"\."))]
      (reduce
        (fn [acc el]
          (condp #(re-matches %1 %2) (last acc)
            #"^$" [el]
            #"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}"
            (let [arr-l (map parse-int (to-array (last acc)))
                  arr-r (map parse-int (to-array el))]
              (if (and
                    (= (take 3 arr-l) (take 3 arr-r))
                    (= (inc (last arr-l)) (last arr-r)))
                (conj (vec (butlast acc))  (str (last acc) "-" (last arr-r)))
                (conj (vec acc) el)))
            #"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}-\d{1,3}"
            (let [arr-l (to-array (last acc))
                  arr-r (map parse-int (to-array el))]
              (if (and
                    (= (take 3 (map parse-int arr-l)) (take 3 arr-r))
                    (= (-> arr-l last last str parse-int inc) (last arr-r)))
                (conj (vec (butlast acc)) (str (-> (last acc) butlast str/join) (last arr-r)))
                (conj (vec acc)  el)))
            (conj (vec acc) el)))
        [""] ips))
    ips))