Executable Code Katas

Use the offline labs for precise contracts and a public checker. Implement four functions: growth_trace, lower_bound, schedule_count, and schedule_value. Source, starter, reference, and evidence template are included in the download.

Before code, submit the cost model, search invariant/variant, greedy exchange argument, and DP state/recurrence. After code, retain checker output and the deterministic report. The checker permits different optimal witnesses and independently validates their feasibility and score.

Introduce two temporary defects deliberately: use earliest-finish greedy for weighted jobs, and treat touching endpoints as incompatible. Predict a counterexample before testing, observe the failure, restore the correct implementation, and retain the explanation. Do not submit the deliberately broken version.

For recurrence-to-code practice, complete C4's memoized and tabulated coin change. No special library is needed. Extend tests with unreachable amounts and an empty coin set (only amount0 is reachable). Require positive denominations so recursion decreases; zero or negative denominations require a different specification.

Completion requires the assessment rubric, not simply green output. Record reference consultation and assistance; recheck a changed case unaided after feedback.