day8.clj

(ns aoc.day8
  [:require [clojure.string :as str]])

(def input 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")

(defn transpose [m]
  (into [] (apply map vector m)))

(defn parse-input [input]
  (let [grid (->> (str/split-lines input)
                  (mapv (fn [line]
                          (->> (partition 1 line)
                               (map (comp parse-long str first)))))
                  (mapv vec))]
    {:original grid
     :transposed (transpose grid)}))

(defn width [grid]
  (-> (:original grid)
      (first)
      (count)))

(defn height [grid]
  (-> (:original grid)
      (count)))

(defn right [grid x y]
  (subvec (get-in grid [:original y]) x))

(defn left [grid x y]
  (reverse (subvec (get-in grid [:original y]) 0 (inc x))))

(defn up [grid x y]
  (reverse (subvec (get-in grid [:transposed x]) 0 (inc y))))

(defn down [grid x y]
  (subvec (get-in grid [:transposed x]) y))

(defn visible? [xs]
  (let [[x & xs] xs]
    (->> (map (partial > x) xs)
         (every? true?))))

(defn part1 []
  (let [grid (parse-input input)]
    (->> (for [x (range (width grid))
               y (range (height grid))]
           (or (visible? (up grid x y))
               (visible? (right grid x y))
               (visible? (down grid x y))
               (visible? (left grid x y))))
         (filter true?)
         (count))))

(defn scenic-score [grid x y]
  (let [score (fn [[x & xs]]
                (->> (split-with (partial > x) xs)
                     ((fn [[xs ys]]
                        (+ (count xs) (min (count ys) 1))))))]
    (* (score (up grid x y))
       (score (right grid x y))
       (score (down grid x y))
       (score (left grid x y)))))

(defn part2 []
  (let [grid (parse-input input)]
    (->> (for [x (range (width grid))
               y (range (height grid))]
           (scenic-score grid x y))
         (sort)
         (last))))