do day 2

2025/src/day02.clj

@@ -0,0 +1,55 @@
+(ns day02
+  (:require
+   [clojure.string :as str]
+   input-manager))
+
+(defn split-comma [s] (str/split s #","))
+
+(def input (->> (input-manager/get-input-raw 2025 2)
+                #_"11-22,95-115,998-1012,1188511880-1188511890,222220-222224,1698522-1698528,446443-446449,38593856-38593862,565653-565659,824824821-824824827,2121212118-2121212124"
+                split-comma
+                (map (comp #(map parse-long %)
+                           #(str/split % #"-")))))
+
+(defn splitable-num? [n]
+  (let [s (str n)
+        len (count s)
+        parition (int (/ len 2))]
+    (and (even? len)
+         (= (.substring s 0 parition) (.substring s parition)))))
+
+;; part 1
+(->> input
+     (map (fn [[a b]]
+            (filter splitable-num? (range a (inc b)))))
+     (mapcat identity)
+     (apply +))
+
+(defn repeated-num? [n]
+  (let [s (str n)
+        len (count s)]
+    (loop [L 1]
+      (cond
+        ;; Stop if the potential substring length L exceeds half the total length
+        ;; (a repetition must be at least twice the substring length)
+        (> L (/ len 2)) false
+
+        ;; Check if L is a divisor of len. If not, this L can't form a full repetition.
+        (not= (mod len L) 0) (recur (inc L))
+
+        ;; L is a divisor. Check if the string is formed by repeating the first L characters.
+        :else
+        (let [substring (subs s 0 L)
+              num-repetitions (/ len L)
+              repeated-string (apply str (repeat num-repetitions substring))]
+          (if (= s repeated-string)
+            true
+            (recur (inc L))))))))
+
+;; part 2
+(->> input
+     (map (fn [[a b]]
+            (filter repeated-num? (range a (inc b)))))
+     (mapcat identity)
+     (apply +))
+