AOC 2020 - Day 5

day5.clj

(require '[clojure.string :as str])

(defn binary-partition [b-string]
  (let [bits (dec (count b-string))]
    (->> b-string
         (map-indexed (fn [i x]
                        (if (#{\B \R} x)
                          (Math/pow 2 (- bits i))
                          0)))
         (reduce +))))

(defn seat-id [a-string]
  (let [rows (drop-last 3 a-string)
        cols (take-last 3 a-string)]
    (+ (* 8 (binary-partition rows))
       (binary-partition cols))))

(defn part-1 []
  (let [data (-> (slurp (format "./inputs/day5.txt"))
                 (str/split-lines))]
    (map seat-id data)))


(defn part-2 []
  (let [seat-ids (sort (part-1))]
    (loop [c (rest seat-ids)
           i (first seat-ids)]
      (if (= (first c) (inc i))
        (recur (rest c) (first c))
        (inc i)))))