From 5366c4c09e946c108b184e4734483bcbb0501164 Mon Sep 17 00:00:00 2001
From: Adam Jeniski <adam.jeniski@flashtalking.com>
Date: Mon, 4 Dec 2023 01:11:19 -0500
Subject: [PATCH] do day 4

---
 2023/src/day04.clj | 49 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 2023/src/day04.clj

diff --git a/2023/src/day04.clj b/2023/src/day04.clj
new file mode 100644
index 0000000..ddc873b
--- /dev/null
+++ b/2023/src/day04.clj
@@ -0,0 +1,49 @@
+(ns ^{:doc "Day 4"
+      :author "Adam Jeniski"}
+ day04 (:require
+        [clojure.math :as math]
+        [clojure.set :refer [intersection]]
+        [clojure.string :as string]
+        [core :refer [get-puzzle-input]]))
+
+(def lines (get-puzzle-input 4))
+
+(defn parse-nums [nums]
+  (->> (string/split nums #" ")
+       (filter not-empty)
+       (map #(Integer/parseInt %))
+       (into #{})))
+
+;; part 1
+(->> lines
+     (map #(re-find #"^Card\s*\d+: ([\s\d]+) \| ([\s\d]+)" %))
+     (map rest)
+     (map (partial map parse-nums))
+     (map (partial apply intersection))
+     (map count)
+     (map #(math/pow 2 (dec %)))
+     (map int)
+     (reduce +))
+
+;; part 2
+(loop [acc 0
+       data (->> lines
+                 (map #(re-find #"^Card\s*\d+: ([\s\d]+) \| ([\s\d]+)" %))
+                 (map rest)
+                 (map (fn [[win actual]]
+                        [1 (count (intersection (parse-nums win)
+                                                (parse-nums actual)))]))
+                 (into []))]
+  (if (not-empty data)
+    (let [cnt-to-add (second (first data))
+          curr-cnt (ffirst data)]
+
+      (recur
+       (+ acc curr-cnt)
+       (concat (->> data
+                    rest
+                    (take cnt-to-add)
+                    (map #(update % 0 + curr-cnt)))
+               (drop (inc cnt-to-add) data))))
+    acc))
+