From e294402b6a64c2d09d6bc68f868c43f3ba63ea52 Mon Sep 17 00:00:00 2001
From: Leah Neukirchen <leah@vuxu.org>
Date: Sat, 12 Dec 2020 21:20:14 +0100
Subject: day10

---
 day10.clj | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 day10.clj

(limited to 'day10.clj')

diff --git a/day10.clj b/day10.clj
new file mode 100644
index 0000000..255ba27
--- /dev/null
+++ b/day10.clj
@@ -0,0 +1,31 @@
+(def data
+  (->> (slurp "day10")
+       (clojure.string/split-lines)
+       (map read-string)
+       vec))
+
+(def diff
+  (->> data
+       (#(cons 0 %))
+       (#(cons (+ 3 (reduce max %)) %))
+       sort
+       (#(map - (rest %) %))))
+
+(->> diff
+     frequencies
+     (#(map % [1 3]))
+     (apply *)) ; => 1820
+
+(->> diff
+     (partition-by identity)
+     (filter #(= (first %) 1))
+     (map count)
+     (map #(inc (* (dec %) (/ % 2))))   ; http://oeis.org/A000124
+     (apply *)) ; => 3454189699072N
+
+;; => (1 3 1 1 1 3 1 1 3 1 3 3)
+;;      1     4      2    1
+;;
+;; => (1 1 1 1 3 1 1 1 1 3 3 1 1 1 3 1 1 3 3 1 1 1 1 3 1 3 3 1 1 1 1 3)
+;;        7         7          4      2         7      1        7
+;; 19208: 2 2 2 7 7 7 7
-- 
cgit 1.4.1