aoc_2021_2.clj

(defn parse-input [input]
  (->> input
       (str/split-lines)
       (map #(let [[v n] (str/split % #" ")]
               [v (Integer/parseInt n)]))))

(defn part-1 [input]
  (->> (parse-input input)
       (reduce (fn [[h d] [v n]]
                 (case v
                   "forward" [(+ h n) d]
                   "down" [h (+ d n)]
                   "up" [h (- d n)]))
               [0 0])
       (apply *)))

(defn part-2 [input]
  (->> (parse-input input)
       (reduce (fn [[h d a] [v n]]
                 (case v
                   "forward" [(+ h n) (+ d (* a n)) a]
                   "down" [h d (+ a n)]
                   "up" [h d (- a n)]))
               [0 0 0])
       (take 2)
       (apply *)))