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@st3fan
Last active December 3, 2020 16:03
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(ns advent-of-code.day3
(:require [advent-of-code.util :as util]))
(defn load-map []
(let [input (doall (util/load-input 3 seq))]
{:data input
:width (count (first input))
:height (count input)}))
(defn at-bottom [map y]
(>= y (:height map)))
(defn has-tree [map x y]
(let [line (nth (:data map) y)]
(= \# (nth line (mod x (:width map))))))
(defn encountered-trees [map [slope-x slope-y]]
(loop [x 0 y 0 c 0]
(if (at-bottom map y)
c
(recur (+ x slope-x) (+ y slope-y) (+ c (if (has-tree map x y) 1 0))))))
(defn part1 []
(let [map (load-map)]
(encountered-trees map [3 1])))
(defn part2 []
(let [m (load-map) slopes [[1 1] [3 1] [5 1] [7 1] [1 2]]]
(apply * (map #(encountered-trees m %) slopes))))
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