Count users over n connections
Company: Coinbase
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: Medium
Interview Round: Technical Screen
Given a stream of relationship events in the form [[user_a, user_b, op], ...], where op ∈ {"connect", "disconnect"}, treat connections as undirected edges. Process events in order, updating the current graph. After all events, return the count of users whose number of current connections is strictly greater than a given integer n. Specify and implement an efficient approach that handles up to 100,000 events and users appearing lazily.
Quick Answer: This question evaluates a candidate's ability to process dynamic graphs and maintain degree counts under a stream of relationship events, covering coding and algorithms, stream processing, and appropriate data structure selection for scalability.