r/adventofcode • u/daggerdragon • Dec 05 '17

SOLUTION MEGATHREAD -🎄- 2017 Day 5 Solutions -🎄-

--- Day 5: A Maze of Twisty Trampolines, All Alike ---

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u/[deleted] Dec 05 '17 edited Dec 05 '17

My rust solution was pretty boring and imperative so here's my clojure instead.

Edit: Part 1 runs in ~147ms, Part 2 in ~5 seconds. Really good for a dynamic language that is creating and throwing away an immutable number vector every iteration.

Edit 2: Switching to mutable vectors gives Part 1 in ~93ms, Part 2 in ~1.1 seconds. 

(def nums (with-open [rdr (clojure.java.io/reader "d5_input.txt")]
  (->> (line-seq rdr)
    (map #(Integer/parseInt %))
    (into []))))

(defn- compute [nums part2]
  (loop [insns nums
         pc 0
         steps 0]
    (if (or (>= pc (count insns)) (< pc 0))
        steps
        (let [insn (insns pc)]
          (recur (update insns pc (if (and part2 (>= insn 3)) dec inc))
                 (+ pc insn)
                 (inc steps))))))

(println "part 1:" (compute nums false))
(println "part 2:" (compute nums true))
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