AOC 2020 Day 3

day_3.clj

(ns day-3
  (:require [clojure.string :as str]))

(def data (-> "input/day_3.txt"
              (slurp)
              (str/split-lines)))


(defn path [dx dy data]
  (first
    (reduce
      (fn [[result-vec row-index] row]
        [(conj result-vec (nth (cycle row) row-index))
         (+ row-index dx)])
      [[] 0]
      (take-nth dy data))))

(defn tree-count [dx dy data]
  (count (filter #(= \# %) (drop 1 (path dx dy data)))))

(comment
  (tree-count 3 1 data))

;; part 2

(def slopes [[1 1]
             [3 1]
             [5 1]
             [7 1]
             [1 2]])

(comment
  (reduce * (map (fn [[dx dy]] (tree-count dx dy data)) slopes)))