Detect repeated visits and cycles
See this course’s project requirements
A runnable fictional help-desk simulator with an undo stack, FIFO queue and small dependency graph, plus empty and cyclic case tests.
Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.
What to include
- An operation-to-structure map with three distinct retrieval rules.
- An undo trace with last-in-first-out and empty-state handling.
- A FIFO record with clear empty behavior.
- A four-node dependency plan ending with archive.
- A cycle diagnosis and justified repair record.
- A runnable stack/queue/dependency demonstration with boundary evidence.
Review and revise
Use these criteria to check your work and choose what to improve.
- The implementation or declared simulation follows the supplied contract and retains inspectable original inputs.
- Normal, boundary and rejected cases are recorded with expected versus observed results.
- The changed case has a correct explanation and does not rely on hidden state.
- The project includes source, outputs, instructions and honest tool, privacy and verification limits.
Want more background?
The idea in everyday life
A depends on B and B depends on A. The supplied graphlib example raises CycleError.
A cycle makes a prerequisite schedule impossible: each member waits for another. Do not hide a cycle by marking a blocked task completed. A visited set also prevents repeatedly traversing the same node.
Detect repeated visits and cycles — original worked practice
A cycle makes a prerequisite schedule impossible: each member waits for another. Do not hide a cycle by marking a blocked task completed. A visited set also prevents repeatedly traversing the same node.
A depends on B and B depends on A. The supplied graphlib example raises CycleError.
1. Step 1
Draw the two opposing prerequisites.
You should see: A→B→A is a cycle.
This keeps the rule and its observable result together.
2. Step 2
Attempt a topological order and record the exception type.
You should see: CycleError identifies that no dependency-respecting order exists.
This keeps the rule and its observable result together.
3. Step 3
Remove B’s dependency on A only when the supplied policy permits it.
You should see: B can precede A after that explicit rule revision.
This keeps the rule and its observable result together.
4. Step 4
Keep the failed and revised graphs and explain the changed rule.
You should see: A cycle diagnosis and justified repair record.
This keeps the rule and its observable result together.
What to finish
A cycle diagnosis and justified repair record.
Watch for this
Calling every repeated node a cycle; a shared predecessor can recur in a valid directed acyclic graph.
How can I tell I understand it?
Explain and demonstrate the required distinction: A cycle makes a prerequisite schedule impossible: each member waits for another. Do not hide a cycle by marking a blocked task completed. A visited set also prevents repeatedly traversing the same node. Show a changed input and the expected result without weakening this contract.
Quick knowledge check
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Source & access notes · checked 2026-10-01
Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.
Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.
Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.
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