init day 8

2024/src/day08.clj

@@ -0,0 +1,44 @@
+(ns day08
+  (:require
+   [core :as c]
+   [input-manager :refer [get-input]]
+   [clojure.math.combinatorics :as combo]
+   [clojure.set :refer [union]]))
+
+(def input (mapv vec (get-input 8)))
+
+(defn get-char [[row col]]
+  (get (get input row) col))
+
+(def locs (->> input
+               c/get-coords
+               (map #(vector (get-char %) %))
+               (group-by first)
+               (#(dissoc % \.))
+               (#(update-vals % (partial mapv second)))))
+
+(defn get-antinode-pos [[x1 y1] [x2 y2] multiplier]
+  (vector (+ x1 (* multiplier (- x2 x1)))
+          (+ y1 (+ (* multiplier (- y2 y1))))))
+
+(defn get-antinodes [[a b]]
+  (filterv #(get-char %) [(get-antinode-pos a b 2) (get-antinode-pos b a 2)]))
+
+;; part 1
+(->> locs
+     vals
+     (map #(->> (combo/combinations % 2) (mapcat get-antinodes) set))
+     (reduce union)
+     (count))
+
+(defn get-antinodes-2 [[a b]]
+  (concat (take-while get-char (map #(get-antinode-pos a b %) (range)))
+          (take-while get-char (map #(get-antinode-pos b a %) (range)))))
+
+;; part 2
+(->> locs
+     vals
+     (map #(->> (combo/combinations % 2) (mapcat get-antinodes-2) set))
+     (reduce union)
+     (count))
+