init day 6

2024-12-06 09:33:17 -05:00
parent 29bf59df8f
commit d40e6cfcd8
2 changed files with 196 additions and 0 deletions
@@ -0,0 +1,66 @@
+(ns day06
+  (:require [input-manager :refer [get-input]]
+            [core :as c]))
+
+(def input (mapv vec (get-input 6)))
+
+(defn get-char [[row col]]
+  (get (get input row) col))
+
+(def start (->> (c/get-coords input)
+                (filter #(= \^ (get-char %)))
+                first))
+
+(def num-cols (count (first input)))
+(def num-rows (count input))
+
+(defn move [dir [row col]]
+  (condp = dir
+    :up [(dec row) col]
+    :down [(inc row) col]
+    :left [row (dec col)]
+    :right [row (inc col)]))
+
+(defn turn-right [dir]
+  (condp = dir
+    :up :right
+    :right :down
+    :down :left
+    :left :up))
+
+(defn in-bounds? [[row col]]
+  (and (>= row 0) (>= col 0) (< row num-rows) (< col num-cols)))
+
+(defn get-path []
+  (loop [pos start
+         dir :up
+         path #{}]
+    (if (not (in-bounds? pos))
+      path
+      (if (path [dir pos])
+        :cycle
+        (let [pos' (move dir pos)]
+          (if (= (get-char pos') \#)
+            (recur pos (turn-right dir) (conj path [dir pos]))
+            (recur pos'
+                   dir
+                   (conj path [dir pos]))))))))
+
+(defn add-obstacle [[row col]]
+  (update input row assoc col \#))
+
+;; part 1
+(->> (get-path)
+     (map second)
+     distinct
+     count)
+
+;; part 2
+(->> (for [pos (->> (get-path)
+                  (map second)
+                  distinct
+                  (filter #(not= % start)))]
+       (with-redefs [input (add-obstacle pos)] (get-path)))
+     (filter #(= % :cycle))
+     count)
+