The core idea clicked pretty fast once I thought about it as a load balancing problem.
Clarify the requirements and constraints, then design a data structure that efficiently tracks the number of sessions per server and the total sessions. Use a greedy assignment strategy: assign each new session to the server with the fewest sessions, ensuring the difference between any two servers never exceeds one. Discuss time and space complexity, and consider edge cases like server failures or dynamic server counts.
Pro tip: Mention that this is essentially a load balancing problem and that a min-heap can efficiently track the least loaded server, but since the difference is bounded by one, a simple round-robin approach also works. Also, discuss how to handle concurrent session starts and potential race conditions.
Ask about the number of servers, whether it's fixed or dynamic, and if sessions can end. Confirm that the goal is to maintain balance with at most one session difference.
Decide on a data structure to track sessions per server. A min-heap of server loads or a simple array with a pointer for round-robin can work. Consider trade-offs.
For start_session, assign to the server with the minimum load. For get_allocation, return the current distribution. Ensure the invariant holds after each assignment.
Discuss time and space complexity. With a heap, start_session is O(log N); with round-robin, O(1). get_allocation is O(N) to return the list.
Consider scenarios like no servers, many sessions, server failures, and concurrency. Propose solutions like locking or atomic operations.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.