⚡ Bolt: [performance improvement] Replace O(N*M) nested loop with O(N) hash map lookup in MaterialExtractor and RAGIndexer

.jules/bolt.md

@@ -6,3 +6,7 @@
 ## 2025-05-20 - Pre-compiling Regex in Loops
 **Learning:** `re.findall(pattern, string)` recompiles (or retrieves from cache) the pattern on every call. In high-frequency functions called inside loops (like complexity estimation), this overhead adds up.
 **Action:** Always pre-compile regexes (`re.compile`) into module-level or class-level constants if they are used repeatedly, especially in tight loops or recursive functions.
+
+## 2025-05-22 - Nested List Search Complexity
+**Learning:** O(N*M) nested loops to find items by key (like matching exercises to solutions) can become a significant bottleneck as dataset sizes grow. In Python, constructing an intermediate lookup dictionary is extremely fast and scales significantly better, reducing lookup from O(N*M) to O(N).
+**Action:** When finding matching items across two lists by a common key, always prefer a pre-computed dictionary (`{item['key']: item for item in list}`) for O(1) lookups instead of nested loops. If there are duplicates and the original code relied on breaking on the first match, construct the dictionary explicitly checking `if key not in dict: dict[key] = item`.