Day 2: Part 2

day2/main.py

@@ -1,9 +1,15 @@
-def is_invalid_id(n: int) -> bool:
+def is_invalid_part2(n: int) -> bool:
     s = str(n)
-    if len(s) % 2 != 0:
+    L = len(s)
+    for k in range(1, L // 2 + 1):
+        if L % k != 0:
+            continue
+        block = s[:k]
+        if block[0] == "0":
+            continue
+        if block * (L // k) == s:
+            return True
     return False
-    half = len(s) // 2
-    return s[:half] == s[half:]
 
 
 total = 0
@@ -14,7 +20,7 @@ with open("input.txt") as f:
 for part in line.split(","):
     lo, hi = map(int, part.split("-"))
     for n in range(lo, hi + 1):
-        if is_invalid_id(n):
+        if is_invalid_part2(n):
             total += n
 
 print(total)