day9.clj

(defn solve1 [input]
  (loop [s       (vec (reverse input))
         lvl     0
         garbage false
         gc      0
         total   0]
    (if-let [c (peek s)]
      (if garbage
        (case c
          \> (recur (pop s) lvl false gc total)
          \! (recur (pop (pop s)) lvl garbage gc total)
          (recur (pop s) lvl true (inc gc) total))
        (case c
          \{       (recur (pop s) (inc lvl) garbage gc total)
          \}       (recur (pop s) (dec lvl) garbage gc (+ total lvl))
          \<       (recur (pop s) lvl true gc total)
          (recur (pop s) lvl garbage gc total)))
      [garbage gc lvl total])))