Represent a Graph with Neighbor Lists
Use the listed edges to identify direct neighbors.
About 22 minutes, plus any extended practice
Supplied materials
- Paper and pencil; answers may also be spoken or typed.
- All cases, labels, numbers and rules are supplied on this page. No real account, private information or purchase is needed.
Learn the idea
A graph represents vertices and edges. A neighbor list records which vertices are directly connected. An edge does not automatically indicate distance or direction unless the model defines those features. The supplied undirected graph is fictional and complete; interpret adjacency rather than a picture’s spacing.
Use the listed edges to identify direct neighbors. Nearby labels on a diagram do not create an edge.
Use this supplied case: Neighbors of A. Undirected edges A-B,A-C,B-D,C-E. Which direct-neighbor set is requested? The task is to connect the given information to the computing idea. Write a short evidence trail so another learner can reproduce your choice. The simplified case describes the stated model, not every real system.
- Represent the supplied worked case with a labeled drawing, table or short trace.
- Use the listed edges to identify direct neighbors.
- Explain why the worked answer fits and why one alternative does not.
- Try the new check and practice cases; revisit the stated rule if your evidence does not match.
See the method in action
The distinct undirected edges are J–K, J–L, K–M and L–N. Put every edge in both endpoint lists: J:[K,L], K:[J,M], L:[J,N], M:[K], N:[L]. K has direct neighbors J and M. N is not a direct neighbor of K: the route K→J→L→N uses intermediate vertices. Nearby labels create no extra edges. These lists represent exactly the supplied connections, not every possible real network.
Check your reasoning
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Helpful tips
- Use the listed edges to identify direct neighbors.
- Nearby labels on a diagram do not create an edge.
See the answer and explanation
A,D
Read A–B, A–C, B–D, and C–E as undirected edges. Put each edge in both endpoint lists: A:[B,C], B:[A,D], C:[A,E], D:[B], E:[C]. B therefore has direct neighbors A and D. E is not a direct neighbor of B; a path from B to E passes through A and C. Nearby labels on a drawing do not create an edge. The list describes exactly the supplied connections, with no inferred extra route. The requested case is: Neighbors of B. Undirected edges A-B,A-C,B-D,C-E. Which direct-neighbor set is requested? Its answer is A,D.
Take it further
New undirected edges P-Q, P-R, R-S. Expected: P neighbors Q, R; S neighbors R only. A visible diagram gap or closeness adds no edge.
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More practice: try new cases
Choose an answer for each problem. Explain your method on paper, then use the feedback to decide what to revisit.
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Check the subject sources
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