m1emi1em.dev
+16
resources/07-test.txt
+16
resources/07-test.txt
···
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.......S.......
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...............
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.......^.......
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...............
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......^.^......
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...............
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.....^.^.^.....
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...............
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....^.^...^....
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...............
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...^.^...^.^...
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...............
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..^...^.....^..
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...............
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.^.^.^.^.^...^.
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...............
+40
src/aoc2025/day7.clj
+40
src/aoc2025/day7.clj
···
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(ns aoc2025.day7
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(:require [aoc2025.util :as util]
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[clojure.set :as set]))
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(defn parse-file [raw-lines]
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(let [[first-row & rest-rows] (mapv util/minv raw-lines)]
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{:start [(some #(if (-> % second (= \S)) (first %) nil) first-row)]
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:splitters (->> rest-rows
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(remove (comp #(= % #{\.}) set #(map second %)))
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(map (partial remove #(-> % second (= \.))))
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(map #(map first %)))}))
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(defn- split-beams [beams splitters]
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(->> (mapcat #(if ((set splitters) %) ((juxt dec inc) %) [%]) beams)
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set
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vec
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sort))
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(defn- unsplit-beams [in-beams out-beams]
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((comp sort vec) (set/intersection (set in-beams) (set out-beams))))
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; [7] [7] => [6 8]
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; [6 8] [6 8] => [5 7 7 9] => [5 7 9]
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(let [grid (->> "07.txt"
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util/read-file
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parse-file)
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;; [first-row & rest-rows] grid
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;; starting-point (get-start first-row)
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;; splitter-indexes (map (partial keep-indexed #(if (= %2 \^) [%1 %2] nil)) rest-rows)
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[_ & beam-splits :as all-beams] (reductions split-beams (:start grid) (:splitters grid))
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]
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(->> (map (fn [in-beams splitters]
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(count (set/intersection (set in-beams) (set splitters))))
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(-> all-beams drop-last)
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(:splitters grid))
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(reduce +)))