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39 lines
1.4 KiB
Clojure
39 lines
1.4 KiB
Clojure
(require '[clojure.string :as str])
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(def input (->> (slurp "./in")
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str/split-lines
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((juxt
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#(let [init-polymer (first %)]
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(for [i (range 0 (dec (count init-polymer)))]
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(subs init-polymer i (+ i 2))))
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(fn [lines]
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(->> lines
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(drop 2)
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(map #(str/split % #" -> "))
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(map (fn [[[a b] c]]
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{(str/join [a b]) (map str/join [[a c] [c b]])}))
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(reduce into)
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))))))
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(def blank-map (zipmap (keys (second input)) (repeat 0)))
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(defn grow-polymer [polymer insertion-rules]
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(reduce
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#(let [[p1 p2] (insertion-rules (key %2)) v (val %2)]
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(-> %1 (update p1 + v) (update p2 + v)))
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blank-map
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(filter (comp pos? val) polymer)))
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(def growth-seq
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(iterate #(grow-polymer % (second input))
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(reduce #(update %1 %2 inc) blank-map (first input))))
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(let [final-polymer (nth growth-seq 40)
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letter-counts (reduce
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(fn [r [k v]] (-> r (update (first k) + v) (update (second k) + v)))
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(zipmap (str/join (keys final-polymer)) (repeat 0))
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final-polymer)
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unique-counts (filter pos? (map #(Math/ceil (/ (val %) 2)) letter-counts))]
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(println (- (apply max unique-counts) (apply min unique-counts))))
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