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(ns org.vuxu.aoc2021.day20
(:require [clojure.string :as str]))
(let [[enhance image] (str/split (slurp "day20") #"\n\n")]
(def enhance (mapv {\# 1 \. 0} enhance))
(def image (mapv (partial mapv {\# 1 \. 0}) (str/split-lines image))))
(defn neighbour-offsets [x y]
(let [digits [-1 0 1]]
(for [dx digits
dy digits]
[(+ x dx) (+ y dy)])))
(defn bin2int [bin]
(Integer/parseInt (apply str bin) 2))
(defn tick [[image i]]
(let [background (if (zero? (enhance 0))
0
(mod i 2))]
[(vec (for [y (range -1 (inc (count image)))]
(vec (for [x (range -1 (inc (count (first image))))]
(enhance (->> (neighbour-offsets y x)
(map #(get-in image % background))
bin2int))))))
(inc i)]))
(def part1
(count (filter (complement zero?)
(flatten (first (nth (iterate tick [image 0]) 2))))))
;; => 5229
(def part2
(count (filter (complement zero?)
(flatten (first (nth (iterate tick [image 0]) 50)))))
;; => 17009
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