Skip to content

Instantly share code, notes, and snippets.

@maacl
Last active December 9, 2022 15:38
Show Gist options
  • Save maacl/992c94a6000ae1ae206a926eccd34294 to your computer and use it in GitHub Desktop.
Save maacl/992c94a6000ae1ae206a926eccd34294 to your computer and use it in GitHub Desktop.
AoC 2022 - Day 9
(ns aoc2022.day9
(:require
[clojure.string :as str]))
(def pos {0 0 1 1 2 1 -1 -1 -2 -1})
(def dirs {"U" [1 0] "R" [0 1] "D" [-1 0] "L" [0 -1]})
(defn move [pos move] (mapv + pos move))
(defn diff [pos1 pos2] (mapv - pos2 pos1))
(defn touching? [d] (#{[0 1] [1 0] [1 1] [0 0]} (mapv abs d)))
(defn positions [f moves] (reductions f [0 0] moves))
(defn moves->1-step-moves
[moves]
(mapcat (fn [[d n]] (repeat (parse-long n) (dirs d))) moves))
(defn H-pos->T-pos
[T-pos H-pos]
(let [d (diff T-pos H-pos)]
(if (touching? d)
T-pos
(move T-pos (mapv pos d)))))
(def common
(->>
(slurp "resources/input9.txt")
str/split-lines
(map #(str/split % #" "))
moves->1-step-moves
(positions move)))
(def end (comp count set))
;; Part 1
(->> common (positions H-pos->T-pos) end)
;; Part 2
(->> common (iterate (partial positions H-pos->T-pos)) (take 10) last end)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment