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(def input-map
(->> (slurp "./in")
(clojure.string/split-lines)
(mapv vec)
(mapv (partial mapv #(- (int %) 48)))
))
(defn basin-bottom-single? [a b]
(if (or (nil? a) (nil? b) (< a b)) 1 0))
(defn basin-continues? [a b]
(and (some? b) (not= b 9) (> b a)))
(defn basin-bottom? [hmap p adj]
(= 4
(apply +
(map
#(basin-bottom-single?
(get-in hmap p)
(get-in hmap %))
adj
))))
(defn get-adj [y x]
[[(dec y) x]
[(inc y) x]
[y (dec x)]
[y (inc x)]])
(defn find-basin [hmap y x adj]
(let [res (reduce
#(if
(basin-continues? (get-in hmap [y x])
(get-in hmap %2))
(conj %1 %2)
%1)
[]
adj
)]
(if (empty? res)
[]
(apply
(partial concat res)
(map
#(find-basin hmap (first %) (second %) (apply get-adj %))
res))
)
)
)
(println
(apply *
(take 3
(sort >
(filter
pos?
(for [y (range 0 (count input-map))
x (range 0 (count (first input-map)))]
(let [adj (get-adj y x)]
(if (basin-bottom? input-map [y x] adj)
(count (distinct (concat [[y x]] (find-basin input-map y x adj))))
0
))))))))
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