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do day 16

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Adam Jeniski 2023-12-16 10:53:27 -05:00
parent 31348da8d4
commit 9b2b3a2c2e
1 changed files with 78 additions and 0 deletions
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2023/src/day16.clj Normal file
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(ns day16 (:require [core :refer [get-puzzle-input]]))
(def input (get-puzzle-input 16))
(def char-map (->> input
(map-indexed (fn [row line]
(map-indexed (fn [col c]
[[row col] c])
line)))
(apply concat)
(into {})))
(def N (count input))
(defn next-loc [{dir :dir
[r c] :loc
:as arg}]
(let [[r' c' :as ans] (condp = dir
:left [r (dec c)]
:right [r (inc c)]
:up [(dec r) c]
:down [(inc r) c])]
(when (and (< -1 r' N)
(< -1 c' N))
(assoc arg :loc ans))))
(defn apply-mirrors [{dir :dir
loc :loc
:as arg}]
(cond (and (#{:left :right} dir)
(= (char-map loc) \|))
(list (assoc arg :dir :up) (assoc arg :dir :down))
(and (#{:up :down} dir)
(= (char-map loc) \-))
(list (assoc arg :dir :left) (assoc arg :dir :right))
(= (char-map loc) \\)
(list (assoc arg :dir (condp = dir
:left :up
:right :down
:up :left
:down :right)))
(= (char-map loc) \/)
(list (assoc arg :dir (condp = dir
:left :down
:right :up
:up :right
:down :left)))
:else (list arg)))
(defn measure-energy [start]
(->> (loop [beams [start]
visited #{}]
(let [beams' (->> (keep next-loc beams)
(map apply-mirrors)
(apply concat)
(filter (complement visited)))]
(if (not-empty beams')
(recur beams'
(apply conj visited beams'))
visited)))
(map :loc)
distinct
count))
;; part 1
(measure-energy {:dir :right
:loc [0 -1]})
;; part 2
(->> [(for [c (range N)] {:loc [N c], :dir :up})
(for [c (range N)] {:loc [-1 c], :dir :down})
(for [r (range N)] {:loc [r -1], :dir :right})
(for [r (range N)] {:loc [r N], :dir :left})]
(apply concat)
(map measure-energy)
(apply max))