aoc2021-day12b Clojure/Babashka program

; SPDX-License-Identifier: MIT
; Copyright (C) 2021 Tito Sacchi <tito@tilde.team>
; WARNING: These solutions were written while I was still learning Clojure and
; should by no means be taken as examples of good programming practice or fast
; implementations.

(ns aoc.2021.12b
  (:require
    [clojure.string :as str]
    [clojure.java.io :as io]))

(def input *in*)

(defn parse-line [l] (str/split l #"-"))
(defn add-edge [edges [v1 v2]]
  (update edges v1 (fnil #(conj % v2) #{})))
(defn small-cave [node] (= node (str/lower-case node)))
(defn implies [x y] (if x y true))
(defn search [edges]
  (loop [queue '([["start" "end"] #{"start"} nil])
         cur-count 0]
    (if (empty? queue) cur-count
      (let [[[start end] visited small-cave-twice]
                      (peek queue)
            popd      (pop queue)
            new-paths (for [neigh (edges start)
                            :let   [updated (if (small-cave neigh)
                                              (conj visited neigh)
                                              visited)
                                    is-snd-visit (visited neigh)]
                            :when  (implies
                                     ; If we already visited some small cave twice,
                                     ; we can't visit any small cave twice anymore.
                                     ; "start" can only be visited once
                                     (or (= neigh "start")
                                         (and
                                           (small-cave neigh)
                                           small-cave-twice))
                                     (not is-snd-visit))]
                        [[neigh end] updated (if is-snd-visit neigh small-cave-twice)])]
        (if (= start end)
          (recur popd (inc cur-count))
          (recur (reduce conj popd new-paths) cur-count))))))

(println (->> input
              (io/reader)
              (line-seq)
              (map parse-line)
              (reduce (fn [edges [v1 v2]]
                        (-> edges
                            (add-edge [v1 v2])
                            (add-edge [v2 v1]))) {})
              (search)))
    

NOTES:
Linux


Sun, 23 Jan 2022 19:25:29 GMT

COMMAND LINE:
bb -f aoc2021_day12b.clj_babashka-1.clj_babashka 0 < aoc2021_day12b-input2.txt

TIMED OUT after 1400s


PROGRAM OUTPUT: