advent-of-code-2023-day3.clj

advent-of-code-2023-day3.clj

(ns advent-of-code-2023.day3)

(defn numbers [s]
  (loop [m (re-matcher #"(?m)\d+" s)
         res {}]
    (if (.find m)
      (recur m (assoc res [(.start m) (.end m)] (Integer. (.group m))))
      res)))

(defn is-part?
  [schematic size [[start end] n]]
  (letfn [(has-sym? [[s e]]
            (when (and (< 0 s (.length schematic))
                       (< 0 e (.length schematic)))
              (boolean
                (re-find #"[^\.\d]" (subs schematic s e)))))]
    (->> [[(- start 1) start]
          [end (+ end 1)]
          [(- start size 1) (- end size -1)]
          [(+ start size -1) (+ end size 1)]]
         (some has-sym?))))

(defn part-sum
  [size schematic]
  (->> schematic
       numbers
       (filter (partial is-part? schematic size))
       vals
       (reduce +)))