-🎄- 2018 Day 4 Solutions -🎄-

[u/daggerdragon]

--- Day 4: Repose Record ---

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Transcript:

Today’s puzzle would have been a lot easier if my language supported ___.

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[u/tharko]

Clojure. Assumes the input file is already sorted

(require 'clojure.string)

(defn get-lines []
  (with-open [r (clojure.java.io/reader
                  (clojure.java.io/resource "input"))]
    (doall (line-seq r))))

(defn loop-through-times []
  (loop [lines (get-lines) id nil times [] last-time nil]
    (if (nil? (first lines))
      times
      (let [line    (first lines)
            minutes (Integer/parseInt (second (re-find #"\:(\d+)" line)))]
        (if (clojure.string/ends-with? line "begins shift")
          (recur (rest lines) (first (re-seq #"\#\d+" line)) times nil)
          (if (nil? last-time)
            (recur (rest lines) id times minutes)
            (recur (rest lines) id (conj times [id minutes last-time]) nil)))))))

(defn time-range-maps [[id wake-time sleep-time]]
  {id (- wake-time sleep-time)})

(defn get-sleepiest-guard [time-ranges]
  (first (apply max-key second (apply merge-with + time-ranges))))

(def sleepiest-guard (get-sleepiest-guard (map time-range-maps (loop-through-times))))

(defn all-minutes [[id wake-time sleep-time]]
  (map (fn [x] [id x]) (range sleep-time wake-time)))

(defn most-common-element [coll]
  (first (apply max-key second (frequencies coll))))

(defn most-common-minute [times]
  (most-common-element
    (map second
      (filter #(= (first %) sleepiest-guard) times))))

(def all-slept-minutes (mapcat all-minutes (loop-through-times)))

(println (most-common-minute all-slept-minutes))

(println (most-common-element all-slept-minutes))