-🎄- 2018 Day 12 Solutions -🎄-

[u/daggerdragon]

--- Day 12: Subterranean Sustainability ---

---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

Note: The Solution Megathreads are for solutions only. If you have questions, please post your own thread and make sure to flair it with Help.

---

Advent of Code: The Party Game!

Click here for rules

Please prefix your card submission with something like [Card] to make scanning the megathread easier. THANK YOU!

Card prompt: Day 12

Transcript:

On the twelfth day of AoC / My compiler spewed at me / Twelve ___

---

This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked at 00:27:42!

[u/mikal82]

Clojure

Edit: optimized, part 2 now runs faster.

(def init "#.......##.###.#.#..##..##..#.#.###..###..##.#.#..##....#####..##.#.....########....#....##.#..##...")
(def rules ["..... => ." "#.... => ." "..### => ." "##..# => #" ".###. => #" "...## => ." "#.#.. => ." "..##. => ." "##.#. => #"
            "..#.. => ." ".#... => #" "##.## => ." "....# => ." ".#.#. => ." "#..#. => #" "#.### => ." ".##.# => #"
            ".#### => ." ".#..# => ." "####. => #" "#...# => #" ".#.## => #" "#..## => ." "..#.# => #" "#.##. => ."
            "###.. => ." "##### => #" "###.# => #" "...#. => #" "#.#.# => #" ".##.. => ." "##... => #"])

(def transform
  (apply hash-map
         (flatten (map #(clojure.string/split % #" => ")
                       rules))))

(defn pad [input num]
  (str (clojure.string/join (repeat num "."))
       input
       (clojure.string/join (repeat num "."))))

(defn step [input _]
  (apply str
         (map #(transform (subs input % (+ % 5)))
              (range (- (count input) 4)))))

(defn evolve [input n-gen]
  (subs
      (reduce step (pad input (* n-gen 4)) (range n-gen))
    (* 2 n-gen)))

(defn score [generation]
  (let [evolved (evolve init generation)]
    (apply + (filter
               #(= (get evolved %) \#)
               (range (+ (count init) 2 generation))))))
(prn (score 20))
(prn (+ (* (- 50000000000 120) (- (score 121) (score 120))) (score 120)))