The DFS framing is a bit of a red herring.
Design a distributed counting algorithm where each node initiates a request to its children via sendAsyncMessage, and children respond with their subtree counts. Aggregate responses at each node to compute the total count, handling asynchronous responses and potential cycles or duplicates.
Pro tip: Use a unique request ID and a visited set to avoid infinite loops in cyclic graphs, and consider using a timeout or retry mechanism for reliability in asynchronous environments.
Ask about the graph structure (tree vs. general graph), whether nodes have unique IDs, and if there are cycles. Confirm that only sendAsyncMessage is available and that receiveMessage is the entry point for incoming messages.
Define message types (e.g., COUNT_REQUEST, COUNT_RESPONSE) and include fields like requestId, senderId, and count. Ensure messages are self-contained and can be correlated.
When a node receives a COUNT_REQUEST, it forwards the request to all neighbors except the sender (or uses a visited set), waits for responses, sums their counts, adds 1 for itself, and sends a COUNT_RESPONSE back. The root initiates the process and aggregates the final count.
Use callbacks, promises, or async/await to manage asynchronous responses. Implement timeouts and retries for unresponsive nodes, and ensure idempotency to handle duplicate messages.
Discuss time complexity (O(n) messages), space complexity (O(n) for visited sets), and edge cases like single node, disconnected components, or cycles. Consider optimizations like batching or gossip protocols.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.