do day 4

2025/src/day04.clj

@@ -0,0 +1,41 @@
+(ns day04
+  (:require input-manager
+            core))
+
+(def input (input-manager/get-input 2025 4))
+
+(def grid (core/map-by-coords input))
+
+(def offsets [[-1 -1] [-1 0] [-1 1]
+              [0 -1]         [0 1]
+              [1 -1]  [1 0]  [1 1]])
+
+;; part 1
+(->> grid
+     (filter (fn [[_ v]]
+               (= v \@)))
+     (map first)
+     (filter (fn [pos]
+               (< (count (filter (comp (partial = \@) grid)
+                                 (for [o offsets]
+                                   (mapv + pos o))))
+                  4)))
+     count)
+
+;; part 2
+(loop [grid grid
+       acc 0]
+  (let [locs
+        (->> grid
+             (filter (fn [[_ v]]
+                       (= v \@)))
+             (map first)
+             (filter (fn [pos]
+                       (< (count (filter (comp (partial = \@) grid)
+                                         (for [o offsets]
+                                           (mapv + pos o))))
+                          4))))]
+    (if (empty? locs)
+      acc
+      (recur (reduce #(dissoc %1 %2) grid locs)
+             (+ acc (count locs))))))