Find frequent IPs from a huge file
Company: Asana
Role: Software Engineer
Category: Software Engineering Fundamentals
Difficulty: medium
Interview Round: Onsite
You are given a very large log file (too large to fit in memory). Each line contains an IPv4 address (e.g., `203.0.113.7`).
Design an approach to answer one of these variants under memory constraints:
- **Variant A:** Find the single most frequent IP.
- **Variant B:** Find the top `K` most frequent IPs.
Explain how you would implement it in practice (data structures, disk usage, complexity), and how your approach changes if:
- Memory is limited to, say, 256MB.
- The file is tens/hundreds of GB.
- You only need an approximate answer.
Overview: This question evaluates a candidate's competency in large-scale data processing and algorithm design, focusing on memory- and disk-constrained frequency estimation, streaming and approximation concepts.