1 files changed, 37 insertions, 0 deletions
diff --git a/day07.clj b/day07.clj
new file mode 100644
index 0000000..be8d66b
--- /dev/null
+++ b/day07.clj
@@ -0,0 +1,37 @@
+(ns org.vuxu.aoc2021.day07
+  (:require [clojure.string :as str]))
+
+(def data
+  (->> (str/split (str/trim-newline (slurp "day07")) #",")
+       (mapv parse-long)))
+
+(defn median [coll]
+  ; only works for even lengths but good enough here
+  (nth (sort coll) (/ (count coll) 2)))
+
+(defn integer-means [coll]
+  (let [mean (/ (apply + coll) (count coll))]
+    [(long (Math/floor mean))
+     (long (Math/ceil mean))]))
+
+(defn abs [n]
+  (Math/abs n))
+
+(defn fuel [n]
+  (* 1/2 n (inc n)))
+
+(def part1
+  (->> data
+       (map (partial - (median data)))
+       (map abs)
+       (apply +)))
+;; => 328187
+
+(def part2
+  (apply min (for [m (integer-means data)]
+               (->> data
+                    (map (partial - m))
+                    (map abs)
+                    (map fuel)
+                    (apply +)))))
+;; => 91257582N