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(require '[clojure.core.reducers :as r])
(def input (->> (slurp "./in")
(clojure.string/split-lines)
(mapv (partial mapv (comp read-string str)))
(#(for [y (range 0 (count %)) x (range 0 (count (first %)))]
{[y x] (get-in % [y x])}))
(into {})))
(defn min-distance [dist Q]
(r/fold
(r/monoid
#(if (< (first %1) (first %2)) %1 %2)
(constantly [##Inf []]))
(r/monoid
#(if (< (first %1) (dist %2)) %1 [(dist %2) %2])
(constantly [##Inf []]))
(r/filter
(partial contains? dist)
(apply vector Q))))
(defn find-neighbors [Q u]
(filter #(contains? Q %) [(update u 0 inc)
(update u 0 dec)
(update u 1 inc)
(update u 1 dec)]))
(let [dim (apply max (map first (keys input)))]
(loop [Q (apply sorted-set (keys input))
dist (assoc (hash-map) [0 0] 0)]
(when (= 0 (rem (count Q) 500)) (println (count Q)))
(if (empty? Q)
(println (dist [dim dim]))
(let [[u vu] (min-distance dist Q)]
(recur
(disj Q vu)
(reduce
#(let [alt (+ u (input %2))]
(cond-> %1
(or (not (contains? dist %2)) (< alt (dist %2)))
(assoc %2 alt)))
dist
(find-neighbors Q vu)))))))
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