advent-10.clj

(ns advent.a10)

(defn look-and-say [ls]
  (flatten (for [l (partition-by identity ls)]
             [(count l) (first l)])))

(defn str->ints [s]
  (map #(Integer/parseInt (str %)) s))

(time
 (let [n 50
       input "1321131112"]
   (count
    (reduce (fn [x _] (look-and-say x)) (str->ints input) (range n)))))

;; ~3 seconds for 40
;; ~60 seconds for 50