From 55f89dc92fe84f528eb7cae3c17178964359e98e Mon Sep 17 00:00:00 2001
From: Jordan Doyle <jordan@doyle.la>
Date: Sun, 10 Dec 2023 03:56:21 +0000
Subject: [PATCH] Add 2022 day 3

---
 2022/3.clj | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100755 2022/3.clj

diff --git a/2022/3.clj b/2022/3.clj
new file mode 100755
index 0000000..bc478b2
--- /dev/null
+++ b/2022/3.clj
@@ -0,0 +1,50 @@
+#!/usr/bin/env nix-shell
+#!nix-shell --pure -i bb -p babashka
+
+(require '[clojure.java.io :as io])
+(require '[clojure.set :as set])
+
+; a-z -> 1->26, A-Z -> 27->52
+(defn char-to-number [char]
+  (cond
+    (Character/isLowerCase char) (- (int char) 96)
+    (Character/isUpperCase char) (- (int char) 38)))
+
+; splits a string into two sets of characters
+(defn split-half [s]
+  (let [idx (quot (count s) 2)
+        [left right] (split-at idx s)]
+    [(set (apply str left)) (set (apply str right))]))
+
+; splits a string in half, stores it in a set and finds the intersection
+(defn part1-process-line [line]
+  (->> (split-half line)
+       (apply set/intersection)))
+
+; processes each line and figures out the "priority" of the intersection
+(defn part1 [lines]
+  (->> lines
+       (map part1-process-line)
+       (mapcat identity)
+       (map char-to-number)
+       (reduce +)))
+
+; processes each line and figures out which characters are shared between
+; 3 lines and sums their "priority"
+(defn part2-process-lines [group]
+  (let [[g1 g2 g3] group]
+    (->> (set/intersection (set g1) (set g2) (set g3))
+         (map char-to-number)
+         (reduce +))))
+
+; splits the input up into 3 lines, processes the "priority" and sums
+(defn part2 [lines]
+  (->> (partition 3 lines)
+       (map part2-process-lines)
+       (reduce +)))
+
+; read the entirety of stdin
+(def lines (with-open [rdr (io/reader *in*)] (vec (->> (line-seq rdr)))))
+
+(println (part1 lines))
+(println (part2 lines))
\ No newline at end of file
--
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