Day 13: Solve part 1 and 2

src/advent_of_code_2023/day13.clj

@@ -1,9 +1,63 @@
 (ns advent-of-code-2023.day13
   (:require
+   [advent-of-code-2023.utils.graph :as g]
    [advent-of-code-2023.utils.string :as u]))
 
-(defn parse-input [input])
+(defn parse-input [input]
+  (mapv #(g/parse-positional-map % identity)
+        (u/split-sections input)))
 
-(defn day13-1 [parsed-input])
+(defn- mirrored?-fn [smudges]
+  (fn [a b]
+    (=
+     (count (filterv (fn [[aa bb]] (not= aa bb))
+                     (mapv vector (take-while (complement nil?) a)
+                           (take-while (complement nil?) b))))
+     smudges)))
 
-(defn day13-2 [parsed-input])
+(defn- vertical-mirror? [{:keys [positions ^long height ^long width]} 
+                         ^long x mirrored?]
+  (let [max-offset (min (inc x) (- width x))]
+    (mirrored?
+     (transduce
+      (mapcat (fn [^long o] (mapv #(positions [(- x o) %]) (range height))))
+      conj [] (range (inc max-offset)))
+     (transduce
+      (mapcat (fn [^long o] (mapv #(positions [(+ (inc x) o) %]) (range height))))
+      conj [] (range (inc max-offset))))))
+
+(defn- horizontal-mirror? [{:keys [positions ^long height ^long width]} 
+                           ^long y mirrored?]
+  (let [max-offset (min (inc y) (- height y))]
+    (mirrored?
+     (transduce
+      (mapcat (fn [^long o] (mapv #(positions [% (- y o)]) (range width))))
+      conj [] (range (inc max-offset)))
+     (transduce
+      (mapcat (fn [^long o] (mapv #(positions [% (+ (inc y) o)]) (range width))))
+      conj [] (range (inc max-offset))))))
+
+(defn- mirrors [{:keys [^long width ^long height] :as p} comp-fn]
+  (let [vertical-candidates
+        (filterv (fn [x] (vertical-mirror? p x comp-fn))
+                 (range (dec width)))
+        horizontal-candidates
+        (filterv (fn [y] (horizontal-mirror? p y comp-fn))
+                 (range (dec height)))]
+    {:vertical-candidates vertical-candidates
+     :horizontal-candidates horizontal-candidates}))
+
+(defn- day13 [mirror-landscape mirrored?]
+  (transduce
+   (comp
+    (map (fn [p] (mirrors p mirrored?)))
+    (map (fn [{:keys [vertical-candidates horizontal-candidates]}]
+           (+ (if-let [v (first vertical-candidates)] (inc ^long v) 0)
+              (* 100 (if-let [h (first horizontal-candidates)] (inc ^long h) 0))))))
+   + mirror-landscape))
+
+(defn day13-1 [mirror-landscape]
+  (day13 mirror-landscape (mirrored?-fn 0)))
+
+(defn day13-2 [mirror-landscape]
+  (day13 mirror-landscape (mirrored?-fn 1)))

test/advent_of_code_2023/day13_test.clj

@@ -4,26 +4,36 @@
    [advent-of-code-2023.day13 :refer :all]
    [advent-of-code-2023.test-utils :as tu]))
 
-(defonce ^:private example-input (parse-input ""))
+(defonce ^:private example-input (parse-input "#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.
+
+#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#"))
 
 (def ^:private input (parse-input (tu/slurp-input "resources/day13.txt")))
 
 (deftest day13-1-example-test
   (testing "day13-1 example"
-    (is (= nil
-           (day13-1 example-input)))))
+    (is (= 405 (day13-1 example-input)))))
 
 (deftest day13-1-test
   (testing "day13-1 example"
-    (is (= nil
-           (day13-1 input)))))
+    (is (= 36041 (day13-1 input)))))
 
 (deftest day13-2-example-test
   (testing "day13-2 example"
-    (is (= nil
-           (day13-2 example-input)))))
+    (is (= 400 (day13-2 example-input)))))
 
 (deftest day13-2-test
   (testing "day13-2 example"
-    (is (= nil
-           (day13-2 input)))))
+    (is (= 35915 (day13-2 input)))))