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(require '[clojure.string :as str])
(def input (->> (slurp "./in")
str/split-lines
((juxt
first
(fn [lines]
(->> lines
(drop 2)
(map #(str/split % #" -> "))
(flatten)
(apply (partial assoc {}))
))))))
(defn grow-polymer [polymer insertion-rules]
(str/join
(cons
(first polymer)
(mapcat (juxt insertion-rules second)
(for [i (range 0 (dec (count polymer)))]
(subs polymer i (+ i 2)))))))
(def growth-seq (iterate #(grow-polymer % (second input)) (first input)))
(let [freqs (vals (frequencies (nth growth-seq 10)))]
(println (- (apply max freqs) (apply min freqs))))
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