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(def to-closing {\{ \} \( \) \[ \] \< \>})
(def to-score {\) 3 \] 57 \} 1197 \> 25137})
(def to-score2 {\) 1 \] 2 \} 3 \> 4})
(defn check-line [input]
(loop [in input open '()]
(if-let [c (first in)]
(if (some->> (#{\} \) \] \>} c) (not= (first open)))
c
(recur
(rest in)
(if-let [op (to-closing c)]
(conj open op)
(rest open)
)))
open
)))
(->> (slurp "./in")
(clojure.string/split-lines)
(map (comp check-line vec))
; check-line returns first invalid character, or list of characters
; necessary to close the line. Work through these through `reduce`
; and build the answers for both parts:
(reduce
(fn [tots nxt]
(if (seq? nxt)
(update tots 1 #(conj % (reduce (fn [a b] (+ (* 5 a) (to-score2 b))) 0 nxt)))
(update tots 0 #(+ % (to-score nxt)))))
[0 '()])
; Get part 2 answer from the list of scores:
(#(update % 1 (fn [ns] (nth ns (quot (count ns) 2)))))
(println))
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