Select low and high character frequencies, choosing the lowest code point in case of a tie

char_counts.clj

(def input "bbbddddaaacccc")
 
(defn- lowest-code-point [coll]
  (first (into (sorted-map-by #(< (int %1) (int %2))) coll)))
 
(defn- take-while= [value coll]
  (take-while (fn [[_ v]] (== value v)) coll))
 
(let [counts (frequencies input)
      sorted (sorted-map-by 
              (fn [k1 k2] 
                (let [v1 (counts k1)
                      v2 (counts k2)]
                  (if (== v1 v2)
                    (.compareTo k2 k1)
                    (.compareTo v2 v1)))))
      sorted-counts (vec (into sorted counts))
      [_ high-count] (first sorted-counts)
      [_ low-count] (last sorted-counts)]
 
  {:high (lowest-code-point (take-while= high-count sorted-counts))
   :low (lowest-code-point (take-while= low-count (reverse sorted-counts)))})

Here's mine https://gist.github.com/clifton/11304681