2023, day 4

Author: FelipeCortez

2023/04.clj

@@ -0,0 +1,45 @@
+(ns scratchcards
+ (:require [clojure.string :as str]
+ [clojure.set :as set]
+ [clojure.math :as math]))
+
+(defn count-winning [line]
+ (let [[_card-number & numbers]
+ (re-seq #"(?:\d+|\|)" line)
+
+ [guessed-numbers _ drawn-numbers]
+ (partition-by (partial = "|") numbers)]
+ (count (set/intersection (set guessed-numbers)
+ (set drawn-numbers)))))
+
+(defn score [winning-count]
+ (if (zero? winning-count)
+ 0
+ (int (math/pow 2 (dec winning-count)))))
+
+;; part 1
+
+(->> (slurp "2023/04.in")
+ (str/split-lines)
+ (map (comp score count-winning))
+ (reduce +))
+
+;; part 2
+
+(defn beget-cards [idx winning count cards]
+ (reduce (fn [cards idx] (update-in cards [idx :count] + count))
+ cards
+ (range (inc idx) (inc (+ idx winning)))))
+
+(let [i (volatile! -1)
+ cards (->> (slurp "2023/04.in")
+ (str/split-lines)
+ (mapv (fn [line] {:winning (count-winning line), :count 1})))]
+ (->> (reduce (fn [cards _]
+ (vswap! i inc)
+ (let [{:keys [winning count]} (get cards @i)]
+ (beget-cards @i winning count cards)))
+ cards
+ (range (count cards)))
+ (map :count)
+ (reduce +)))