do day 7

2025/src/day07.clj

@@ -0,0 +1,55 @@
+(ns day07
+  (:require input-manager
+            core))
+
+(def input (input-manager/get-input 2025 7))
+
+(def start ((core/map-to-coords input) \S))
+(def grid (core/map-by-coords input))
+(def NUM_ROWS (count input))
+
+(defn left [loc] (update loc 1 dec))
+(defn right [loc] (update loc 1 inc))
+(defn down [loc] (update loc 0 inc))
+(defn splitter? [loc] (= (grid loc) \^))
+
+;; part 1
+(->> (range NUM_ROWS)
+     (reduce (fn [{:keys [acc search-locs]} _]
+               (if (empty? search-locs)
+                 (reduced acc)
+                 (let [next-locs (map down search-locs)
+                       splitters (filter splitter? next-locs)
+                       next-locs (-> #{}
+                                     (into (filter (complement splitter?) next-locs))
+                                     (into (mapcat (juxt left right) splitters)))]
+                   {:acc (into acc splitters)
+                    :search-locs next-locs})))
+             {:acc #{}, :search-locs #{start}})
+     :acc
+     count)
+
+(defn left-entry [[loc cnt]] [(left loc) cnt])
+(defn right-entry [[loc cnt]] [(right loc) cnt])
+(defn splitter-entry? [[loc _]] (= (grid loc) \^))
+(defn join-flows [flows]
+  (reduce (fn [acc [loc cnt]]
+            (if (acc loc)
+              (update acc loc + cnt)
+              (assoc acc loc cnt)))
+          {}
+          flows))
+
+;; part 2
+(->> (range NUM_ROWS)
+     (reduce (fn [{:keys [acc search-locs]} _]
+               (if (empty? search-locs)
+                 (reduced acc)
+                 (let [next-locs (update-keys search-locs down)
+                       splitters (filter splitter-entry? next-locs)
+                       next-locs (join-flows (concat (filter (complement splitter-entry?) next-locs)
+                                                     (mapcat (juxt left-entry right-entry) splitters)))]
+                   {:acc (apply + acc (map (fn [[_ cnt]] cnt) splitters))
+                    :search-locs next-locs})))
+             {:acc 1, :search-locs {start 1}})
+     :acc)