migrate 392 questions to pattern format

backend/data/questions/check-distances-between-same-letters.yaml

@@ -8,7 +8,8 @@ categories:
   - strings
   - hash-tables
 patterns:
-  - two-pointers
+  - slug: two-pointers
+    is_optimal: true
 
 function_signature: "def check_distances(s: str, distance: list[int]) -> bool:"