Independent Assessment

Independent transfer

Without copying the reference implementation, build a separate summarize_by_topic variant that also reports a count for each topic. Keep the original lab contract and checker intact. Use an input with two identical records, two topics and an empty-history case. State whether counts represent records or distinct durations and verify input preservation.

Explain a raw-byte change that leaves the logical records unchanged and a logical change that alters the report. Demonstrate one rejected input without source modification.

Submit your code, independently calculated expected results and an explanation of each boundary. Use the rubric, then compare calibration.