2023, day 9

Author: FelipeCortez

2023/09.clj

@@ -0,0 +1,30 @@
+(ns mirage-maintenance
+ (:require [clojure.string :as str]))
+
+(defn differences [xs]
+ (->> xs
+ (partition 2 1)
+ (mapv #(- (second %) (first %)))))
+
+(defn pyramidize [xs]
+ (->> (iterate differences xs)
+ (take-while #(not (= #{0} (set %))))
+ (into [])))
+
+(defn extrapolate [pyramid] (reduce + (mapv peek pyramid)))
+
+(defn parse-line [line] (mapv parse-long (str/split line #"\s")))
+
+(->> (slurp "2023/09.in")
+ (str/split-lines)
+ (mapv parse-line)
+ (mapv (comp extrapolate pyramidize))
+ (reduce +))
+
+;; part 2
+
+(->> (slurp "2023/09.in")
+ (str/split-lines)
+ (mapv parse-line)
+ (mapv (comp extrapolate pyramidize vec reverse))
+ (reduce +))