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I went straight to a hash map and the interviewer kind of waited, like they wanted something more structured.
Start by clarifying requirements and scale, then propose a trie-based data structure to store hierarchical paths, with each node representing a geographic segment. Implement add_path and is_authorized methods, and discuss trade-offs between time and space complexity, as well as potential extensions like caching or distributed storage.
Pro tip: Mention that paths should be normalized (e.g., lowercase, consistent delimiters) to avoid inconsistencies, and consider edge cases like trailing slashes or empty segments. Also, highlight that authorization checks can be optimized by storing permissions at nodes and propagating them.
Ask about expected scale (number of paths, query frequency), whether paths are case-sensitive, and if permissions can be inherited (e.g., /France grants access to /France/Paris).
Propose a trie (prefix tree) where each node represents a path segment, allowing efficient insertion and lookup. Alternatively, consider a hash set with prefix matching, but discuss trade-offs.
Define add_path to insert a path into the trie, marking nodes as authorized. Define is_authorized to traverse the trie and check if the path or any ancestor is authorized.
Discuss time complexity: O(L) for both operations where L is path length, and space complexity O(N*L) for N paths. Compare with alternatives like sorted lists or databases.
Mention potential improvements: caching frequent queries, handling concurrency, distributing the trie, or using a database with materialized paths.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.