Represent dependencies as a graph
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
Graph is {write:[], review:[write], publish:[review]}. These labels are steps, not people or times.
A dependency graph records what must finish first. In graphlib.TopologicalSorter, each dictionary value contains that node’s predecessors, not its successors.
Represent dependencies as a graph — original worked practice
A dependency graph records what must finish first. In graphlib.TopologicalSorter, each dictionary value contains that node’s predecessors, not its successors.
Graph is {write:[], review:[write], publish:[review]}. These labels are steps, not people or times.
1. Step 1
Draw write→review→publish.
You should see: The arrow means must happen before.
This keeps the rule and its observable result together.
2. Step 2
Translate each node into its predecessor set.
You should see: write has none; review has write; publish has review.
This keeps the rule and its observable result together.
3. Step 3
Run or trace static_order().
You should see: write, review, publish is a valid sequence.
This keeps the rule and its observable result together.
4. Step 4
Add archive depending on publish and check the new order.
You should see: A four-node dependency plan ending with archive.
This keeps the rule and its observable result together.
What to finish
A four-node dependency plan ending with archive.
Watch for this
Interpreting a predecessor mapping backwards and trying to publish before review finishes.
How can I tell I understand it?
Explain and demonstrate the required distinction: A dependency graph records what must finish first. In graphlib.TopologicalSorter, each dictionary value contains that node’s predecessors, not its successors. Show a changed input and the expected result without weakening this contract.
Quick knowledge check
Answer all 3 questions. Get at least 2 right and the lesson completes automatically.
You’ll get an explanation for each answer. Signed in? Your results save to your account.
Pass the check. We’ll save the progress.
Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.
Go to the knowledge checkTools, templates, and lesson sources
Tools and templates
Tools open in a new tab so you can keep your place here.
Sources and further reading
Explore the references behind this lesson.
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.
Report a problem with this lesson
Tell us what went wrong. Please leave out personal information and private project contents.