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(ns org.vuxu.aoc2021.day09
(:require [clojure.string :as str]))
(defn parse-digit [char]
(Character/digit char 10))
(def data
(->> (slurp "day09")
(str/split-lines)
(mapv (partial mapv parse-digit))))
(def datamap
(zipmap (for [x (range (count data))
y (range (count (data x)))]
[x y])
(flatten data)))
(def low-points
(filter (fn [[x y]]
(< (get datamap [x y])
(apply min (for [[dx dy] [[-1 0] [1 0] [0 -1] [0 1]]]
(get datamap [(+ x dx) (+ y dy)] 999)))))
(keys datamap)))
(def part1
(->> low-points
(map datamap)
(map inc)
(apply +)))
;; => 512
(defn grow [[x y]]
(->> (for [[dx dy] [[-1 0] [1 0] [0 -1] [0 1]]]
[(+ x dx) (+ y dy)])
(filter (fn [[xx yy]]
(not= 9 (get datamap [xx yy] 9))))))
(defn fix [f x]
(loop [x x]
(let [fx (f x)]
(if (= x fx) x (recur fx)))))
(defn measure [p]
(count (fix (fn [ps] (apply conj ps (mapcat grow ps)))
(set [p]))))
(def part2
(->> low-points
(map measure)
sort
(take-last 3)
(apply *)))
;; => 1600104
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