advent of code 2021 day 5

2021-day5.clj

(ns stuartstein777.2021.day5
  (:require [clojure.string :as str]
            [clojure.set :as set]
            [stuartstein777.file :as f]
            [stuartstein777.utils :as u]))

(defn parser [line]
  (let [[x1 y1 x2 y2] (->> line
                           (re-seq #"(\d+),(\d+) -> (\d+),(\d+)")
                           (u/frest)
                           (map #(Integer/parseInt %)))]
    [[x1 y1] [x2 y2]]))

(defn horizontal-or-vertical? [[[x1 y1] [x2 y2]]]
  (or (= x1 x2) (= y1 y2)))

(defn get-horizontal-or-vertical-points [[[x1 y1] [x2 y2]]]
  (for [xs (range (min x1 x2) (inc (max x1 x2)))
        ys (range (min y1 y2) (inc (max y1 y2)))]
    [xs ys]))

(defn get-diagonal-points [[[x1 y1] [x2 y2]]]
  (cond (and (>= x2 x1) (>= y2 y1)) (map vector (range x1 (inc x2)) (range y1 (inc y2)))
        (and (<= x2 x1) (<= y2 y1)) (map vector (range x2 (inc x1)) (range y2 (inc y1)))
        (and (<= x1 x2) (>= y1 y2)) (map vector (range x1 (inc x2)) (reverse (range y2 (inc y1))))
        (and (>= x1 x2) (<= y1 y2)) (map vector (reverse (range x2 (inc x1))) (range y1 (inc y2)))))

(defn get-points-on-line [coords]
  (if (horizontal-or-vertical? coords)
    (get-horizontal-or-vertical-points coords)
    (get-diagonal-points coords)))

(->> (f/read-all-lines-and-parse "puzzle-inputs/2021/day5" parser)
     #_(filter horizontal-or-vertical?) ; uncomment to solve part 1
     (mapcat get-points-on-line)
     (frequencies)
     (filter (fn [[_ v]] (> v 1)))
     (count))