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Course Schedule
Course Schedule tests whether you can detect a cycle in a directed graph. Model the prerequisites as edges, then topologically sort — Kahn's BFS peeling off zero-indegree nodes, or DFS with a recursion-stack check. Interviewers watch whether you reason cleanly about dependencies and catch the cycle that makes the schedule impossible.
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Graph Interview Questions
BFS explores by layers using a queue; DFS explores deeply using a stack or recursion -- the same traversal with a different container. Choose BFS for shortest-path in unweighted graphs and "minimum steps," DFS for counting components, islands, and tree recursion.
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