do day 3

2023/src/day03.clj

@@ -0,0 +1,72 @@
+  (ns ^{:doc "Day 3"
+        :author "Adam Jeniski"}
+   day03 (:require
+          [core :refer [get-puzzle-input re-seq-pos]]))
+
+(defn parse-nums [line]
+  (re-seq-pos #"\d+" line))
+
+(def lines (get-puzzle-input 3))
+(def char-map
+  (->> lines
+       (map-indexed (fn [row-idx line]
+                      (map-indexed (fn [col-idx char]
+                                     [[row-idx col-idx] char])
+                                   line)))
+       (mapcat identity)
+       (into {})))
+
+(defn touches-symbol? [[row-idx col-idx s]]
+  (let [length (count s)]
+    (->> (for [r [(dec row-idx) row-idx (inc row-idx)]
+               c (range (dec col-idx) (+ col-idx length 1))]
+           (char-map [r c]))
+         (filter (comp not nil?))
+         (some #(not (or (Character/isDigit %) (= % \.)))))))
+
+;; part 1
+(->> lines
+     (map parse-nums)
+     (map-indexed (fn [row matches]
+                    (map #(vector row (:start %) (:group %))
+                         matches)))
+     (mapcat identity)
+     (filter touches-symbol?)
+     (map #(Integer/parseInt (nth % 2)))
+     (reduce +))
+
+(defn touches-star? [[row-idx col-idx s]]
+  (let [length (count s)]
+    (->> (for [r [(dec row-idx) row-idx (inc row-idx)]
+               c (range (dec col-idx) (+ col-idx length 1))]
+           [[r c] (char-map [r c])])
+         (filter #(not (nil? (second %))))
+         (filter #(= \* (second %)))
+         (map #(vector % s)))))
+
+;; part 2
+(let [data (->> lines
+                (map parse-nums)
+                (map-indexed (fn [row matches]
+                               (map #(vector row (:start %) (:group %))
+                                    matches)))
+                (mapcat identity)
+                (map touches-star?)
+                (filter seq)
+                (mapcat identity)
+                (map #(vector (ffirst %) (second %))))
+      cogs (->> data
+                (map first)
+                (frequencies)
+                (filter #(= (second %) 2))
+                (map first)
+                (into #{}))]
+  (->> data
+       (group-by first)
+       (filter #(cogs (first %)))
+       (map #(update % 1 (partial mapv second)))
+       (map second)
+       (map (partial map #(Integer/parseInt %)))
+       (map (partial reduce *))
+       (reduce +)))
+