Module 3: Graph Algorithms & Network Analysis: Mistake Clinic

This clinic turns wrong moves into reusable judgment. Use it after each practice page and again before the quiz or checkpoint.

Module-Specific Mistake Radar

Start with these traps. Replace or extend them with real mistakes from your own work.

Mistake to look for	Where it shows up	Symptom	Repair evidence
Finishing Graph Representation and Traversal Lab with only a final answer	Graph Representation and Traversal Lab	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing Shortest Paths and MST Workshop with only a final answer	Shortest Paths and MST Workshop	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing Network Flow and Matching Clinic with only a final answer	Network Flow and Matching Clinic	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing Code Katas with only a final answer	Code Katas	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Treating What a Graph Is as vocabulary instead of a tool	What a Graph Is	The explanation names the concept but cannot decide between two cases.	Write one example, one non-example, and the rule that separates them.
Treating Adjacency List vs Adjacency Matrix as vocabulary instead of a tool	Adjacency List vs Adjacency Matrix	The explanation names the concept but cannot decide between two cases.	Write one example, one non-example, and the rule that separates them.

Pull any miss from these checks into your mistake log.

For each statement, identify the error:

For each statement, identify the error:

"I ran Dijkstra on a graph with a few negative edges; no negative cycle, so the answers are correct."
"Floyd-Warshall is always better for APSP than running Dijkstra many times."
"Prim gives the shortest path tree from the root."
"Kruskal runs in O(|E| log |V|) even without union by rank and path compression."
"Bellman-Ford detects all negative cycles in the graph."
"Dijkstra with a Fibonacci heap is always the fastest choice in practice."

For each statement, identify the error:

"I counted backward edges T -> S in the cut capacity, so my min-cut is c(S, T) + c(T, S)."
"Ford-Fulkerson always terminates in polynomial time."
"Max flow equals min cut only when the capacities are integers."
"Bipartite matching reduces to shortest paths."
"If there is no augmenting path, I haven't yet found the max flow - I just need to try another DFS order."
"Hopcroft-Karp works because bipartite graphs have no cycles."

For each real mistake:

Reproduce the failure on the smallest example, trace, proof, query, command, or design sketch.
Name the hidden assumption.
Repair the artifact.
Save evidence that changed: failing then passing test, corrected proof step, revised diagram, safer command, benchmark, or review note.
Add one retrieval card beginning with Check... before... or Do not use... when....

Date	Mistake	Symptom	Root cause	Repair evidence	Retrieval card
Starter	Pick one radar row above	Explain how it would fail in this module	Name the assumption	Add a counterexample or corrected artifact	Write the card before closing the page

At least five real mistakes are logged.
At least two mistakes include a counterexample or failing test.
At least one mistake connects to an older semester skill.
At least one correction changes code, a proof, a diagram, a command transcript, a query, or a design decision.