Created
December 20, 2021 18:01
-
-
Save tatut/1233cdcba52cb0b53659535bf975044f to your computer and use it in GitHub Desktop.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
(ns day20 | |
(:require [clojure.java.io :as io])) | |
(def input (-> "day20.txt" io/reader line-seq)) | |
(def enhance-alg (vec (first input))) | |
(def initial-img | |
(into #{} | |
(mapcat identity) | |
(map-indexed | |
(fn [y line] | |
(for [x (range (count line)) | |
:when (= \# (.charAt line x))] | |
[x y])) | |
(drop 2 input)))) | |
(defn bounds | |
"Return [minx miny maxx maxy] for img" | |
[img] | |
(let [xs (map first img) | |
ys (map second img)] | |
[(reduce min xs) (reduce min ys) | |
(reduce max xs) (reduce max ys)])) | |
(defn enhance [img out-lit] | |
(let [[minx miny maxx maxy] (bounds img)] | |
(letfn [(lit [[x y :as p]] | |
(if (and (<= minx x maxx) | |
(<= miny y maxy)) | |
(if (img p) 1 0) | |
out-lit)) | |
(grid-enhance-rule [x y] | |
(reduce #(bit-or (bit-shift-left %1 1) (lit %2)) 0 | |
(for [dy [-1 0 1] dx [-1 0 1]] [(+ x dx) (+ y dy)])))] | |
(into #{} | |
(for [x (range (- minx 1) (+ maxx 2)) | |
y (range (- miny 1) (+ maxy 2)) | |
:when (= \# (enhance-alg (grid-enhance-rule x y)))] | |
[x y]))))) | |
(defn part1 [] | |
(-> initial-img | |
(enhance 0) | |
(enhance 1) | |
count)) | |
(defn part2 [] | |
(count | |
(reduce (fn [img out] | |
(enhance img out)) | |
initial-img | |
(take 50 (cycle [0 1]))))) | |
(time (part1)) ;; 77ms | |
(time (part2)) ;; 2520ms |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment