Learn Inspect algorithms and repair failures with explicit contracts and counterexamples.
Start with everyday situations, predict an outcome, and test your ideas. You need basic arithmetic, percentages and graph reading; explanations introduce additional ideas where needed. No coding or account is required. Every investigation has school, college and workplace extensions—you can choose any of them.
Implement a deterministic tool, inspect algorithmic work, connect records by identity, test failure cases and design bounded retries.
Open any topic directly. Review functions and graphs whenever useful.
The original two-investigation starter remains available. Choosing the full course adds its published lessons to your selected scope; your earlier work stays saved. Skipping does not count as completion or understanding.
Free exploration: no completion scope selected yet. Project reports and independent evidence are tracked separately.
Choose a unit, then open a lesson on its own page. This outline lists the sequence; it does not combine the full lessons into one page.
Implement a calculation and compare algorithms by a named work measure.
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Does changing calculation order preserve the contract?
An original synthetic invoice has base prices 10,20,30. The contract adds percentage tax to each base price, then an untaxed flat fee. Implement the rule in the linked code runner.
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When does dividing the search space save work?
Search an original synthetic sorted inventory of consecutive IDs. Each inspected item counts as one unit of algorithmic work; this is not elapsed computer time.
Use stable keys and test boundaries rather than assuming correct behavior from happy-path output.
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Why does joining rows by position send orders to the wrong person?
Original customers [101 Ada,102 Bo,103 Cy] and orders [103:30,101:10] have different ordering. A second order for customer 103 can be added.
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Can all your tests pass while the rule is wrong?
A synthetic request system must approve quantities at or above a threshold. Choose an implementation and test cases. The controls select predefined rules; no source code is executed.
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Which tests expose a missing input guard?
A synthetic quote function charges 3×quantity+2 for positive quantities and zero otherwise. Its buggy version applies the formula to every quantity.
Distinguish execution from acknowledgment, avoid duplicate effects and bound retries.
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What if a charge succeeds but its response is lost?
A fictional local service records a charge and may lose its response. Retry limits and a simulated idempotency key determine whether duplicates occur.
Write a small program that joins customer IDs to orders, calculates a contract-defined price and reports unmatched inputs. Add independent tests and a local retry simulation that never double-applies the same operation. Work only with invented records.
Save a report, compare captured evidence, and attempt three new cases. A completed report records submitted work; the rubric supports a separate human review of its quality.
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