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41 lines
1.5 KiB
Clojure
41 lines
1.5 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 [[pair ltr]]
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{pair (map str/join [[(first pair) ltr] [ltr (second pair)]])}))
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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 [polymer (nth growth-seq 40)
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results (filter pos?
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(map #(Math/ceil (/ % 2))
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(vals
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(reduce
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#(let [k (key %2) v (val %2)] (-> %1 (update (first k) + v) (update (second k) + v)))
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(zipmap (flatten (map (partial split-at 1) (keys polymer))) (repeat 0))
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polymer))))]
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(println (- (apply max results) (apply min results))))
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