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Graph Algorithms and Traversal Questions

Covers fundamental representations, traversal techniques, and classical algorithms for graph structured data. Candidates should understand graph representations such as adjacency list and adjacency matrix and the tradeoffs in time and space for each. Core traversal skills include implementing and reasoning about breadth first search and depth first search for reachability, traversal order, and unweighted shortest path discovery, as well as tree traversal variants and their relationship to graph traversals. Algorithmic topics include cycle detection, topological sorting for directed acyclic graphs, connected components and strongly connected components, and shortest path and pathfinding algorithms for weighted graphs including Dijkstra algorithm and Bellman Ford algorithm with discussion of negative weights and appropriate use cases. Candidates should be able to analyze time and space complexity, choose appropriate auxiliary data structures such as queues, stacks, priority queues, and union find, handle directed versus undirected and weighted versus unweighted graphs, discuss implementation details and trade offs, and explain practical applications such as dependency resolution, scheduling, pathfinding, connectivity queries, and roles of graph algorithms in system design and data processing.

EasyTechnical
0 practiced
Describe the union-find (disjoint-set) data structure including union by rank and path compression. Explain its amortized time complexity and how you'd use union-find to compute connected components in batch processing of large graphs.
MediumTechnical
0 practiced
Describe and implement the Bellman-Ford algorithm in Python to compute shortest paths from a source node in graphs that may contain negative edge weights. Your implementation should detect negative-weight cycles reachable from the source and report them. Discuss complexity and situations in ETL where Bellman-Ford would be appropriate.
MediumTechnical
0 practiced
Implement Kahn's algorithm for topological sorting in Python. Given a directed graph as an adjacency-list dict, return a topological order if the graph is a DAG or indicate a cycle if not. Explain complexity and how you would make the ordering deterministic across runs.
HardSystem Design
0 practiced
You're responsible for a petabyte-scale graph in a data lake used for both batch analytics and low-latency neighborhood queries. Propose a hybrid storage and indexing strategy (file format, partitioning, adjacency indexing, caches, precomputed neighborhoods) that balances fast k-hop lookups and efficient batch analytics. Describe update and compaction strategies to keep the dataset performant.
EasyTechnical
0 practiced
Explain cycle detection in directed graphs using DFS with node color states (white/gray/black). Describe how back edges are identified and why this method reliably detects cycles even in complex pipeline dependency graphs. Also explain how you would return the actual nodes involved in the detected cycle.

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