Maintain top N payers
Company: Meta
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: Medium
Interview Round: Take-home Project
Implement topNPayers(n) that returns the n accounts with the highest cumulative outgoing payment amounts as strings formatted "{accountId}:{totalOutgoing}". Rank by the sum of amounts from debit operations (e.g., pay, executed scheduled payments). Support online updates as new debits occur. Explain your data structures (e.g., a size-N min-heap or an ordered map), tie-breaking rules, how to handle accounts with equal totals, and the time/space complexity per update and query.
Quick Answer: This question evaluates proficiency in streaming algorithms and data-structure design for maintaining top-k aggregates over transactional data, including handling real-time updates, tie-breaking rules, and time/space complexity reasoning.