← Applied intuition Interview Insights
The ambiguous zone between 200ms and 500ms is what got me.
Start by clarifying requirements and edge cases, then propose a state machine per button that tracks press duration and classifies clicks based on thresholds. Discuss concurrency handling, debouncing, and how to manage consecutive presses without blocking the stream.
Pro tip: Emphasize the importance of non-blocking, event-driven design and mention that thresholds should be configurable to accommodate different hardware and user preferences.
Ask about sampling rate, button count, expected click durations, and how to handle simultaneous presses or rapid consecutive clicks. Confirm whether classification should be real-time or after release.
Define states (IDLE, PRESSED, LONG_PRESS) and transitions based on sample values and elapsed time. Use timestamps to measure duration and classify on release or when threshold is exceeded.
Maintain separate state for each button, process samples in a single loop or via event-driven callbacks. Ensure thread safety if using multiple threads, or use a single-threaded event loop for simplicity.
Implement debouncing to ignore spurious transitions and reset state after each click. For consecutive presses, ensure the state machine can handle a new press immediately after release without losing events.
Compare polling vs. interrupt-driven approaches, memory vs. accuracy, and configurability of thresholds. Mention potential issues like missed samples or timing jitter and how to mitigate them.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.