From adfc073ed1942fdc80183aac4f09ba2f245c5dd6 Mon Sep 17 00:00:00 2001
From: Adam Jeniski <adam.jeniski@flashtalking.com>
Date: Fri, 15 Dec 2023 15:27:48 -0500
Subject: [PATCH] do day 15

---
 2023/src/day15.clj | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 2023/src/day15.clj

diff --git a/2023/src/day15.clj b/2023/src/day15.clj
new file mode 100644
index 0000000..df080df
--- /dev/null
+++ b/2023/src/day15.clj
@@ -0,0 +1,41 @@
+(ns day15 (:require [clojure.string :as str]
+                    [core :refer [get-puzzle-input]]))
+
+(def input (-> (first (get-puzzle-input 15))
+               (str/replace #"\n" "")
+               (str/split #",")))
+
+(defn HASH [s]
+  (reduce (fn [acc el] (mod (* 17 (+ el acc)) 256))
+          0
+          (map int s)))
+
+;; part 1
+(->> (map HASH input)
+     (reduce +))
+
+;; part 2
+(->> input
+     (map (juxt #(re-find #"[a-zA-Z]+" %)
+                #(re-find #"[0-9]+" %)))
+     (map #(->> (first %) HASH (assoc % 2)))
+     (reduce (fn [m [label lens box]]
+               (if lens
+                 (if (some #(= (first %) label)
+                           (m box))
+                   (update m box (partial mapv #(if (= (first %) label)
+                                                  [label lens]
+                                                  %)))
+                   (update m box conj [label lens]))
+                 (update m box (partial filterv #(not= (first %) label)))))
+             (->> (range 5)
+                  (map #(vector % []))
+                  (into {})))
+     (map (fn [[box l]]
+            (map-indexed (fn [idx el]
+                           (* (inc idx)
+                              (inc box)
+                              (parse-long (second el))))
+                         l)))
+     (apply concat)
+     (reduce +))