← Databricks Interview Insights
The parsing part was fine, converting each CIDR block to a network and prefix length or a start/end interval isn't that bad.
Clarify the problem constraints (e.g., number of rules, whether rules are ordered, and if overlapping rules are possible) before designing a solution. Then propose an efficient algorithm, such as converting CIDR blocks to integer ranges and using interval trees or sorting for lookup, and discuss trade-offs between preprocessing time and query time.
Pro tip: Mention that CIDR rules can be converted to integer ranges and that the longest prefix match (most specific rule) should take precedence, which is common in networking. Also, discuss how to handle overlapping rules and the importance of clarifying the expected behavior with the interviewer.
Ask about the number of rules, query frequency, whether rules are ordered, and how to handle overlapping rules (e.g., longest prefix match or first match).
Consider converting CIDR blocks to integer ranges and using interval trees, sorted arrays with binary search, or a trie for efficient lookup.
Outline steps: parse CIDR to range, build data structure, and for a query IP, find matching rules and apply precedence to decide approve/reject.
Discuss time and space complexity for preprocessing and querying, and compare trade-offs between different approaches.
Address edge cases like no matching rule (default action?), invalid IPs, and overlapping rules with different labels.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.