CMP.2:8 - Common Anti-Patterns and How to Avoid Them

Misstep exposed by the method	Consequence and repair
Return only the final scalar from each part	The segment example loses crossing answers. Derive the join and retain the boundary summaries it consumes.
Treat a changed input as a smaller input	Calls can continue indefinitely. State a well-founded decrease and check every recursive branch against it.
Treat termination as affordability	An exponential call tree can terminate correctly. Count calls and local work; share repeated subproblems when useful.
Keep the old summary after changing the question	A length constraint or witness request can be lost. Reconstruct what the new join needs and revise the affected result.