Implement a multi-button click detector

Q: Implement a multi-button click detector

This question evaluates competency in real-time event stream processing, per-button state management, and timing-based classification of input events such as distinguishing single versus long presses.

Q: How do I approach Coding & Algorithms interview questions?

Coding & Algorithms questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master coding & algorithms interviews.

Question

Implement a click detector for multiple physical buttons.

You receive button state updates as a stream. Each update provides:

button_id (integer)
state where 1 = pressed , 0 = released
(initially) updates arrive every 10 ms per button (you may assume updates are ordered in time).

A “click” is a press followed by a release. Classify each completed click as:

Single Click : press duration ≤ 200 ms
Long Click : press duration ≥ 500 ms

For each detected click, output something like:

Button 1: Single Click
Button 2: Long Click

Requirements / edge cases:

Support multiple buttons concurrently.
Handle back-to-back clicks on the same button (press/release cycles repeated over time).
Handle no click (e.g., no transitions) without producing output.
Clarify/handle what to do for press durations in the (200 ms, 500 ms) gap.

Follow-up: If state updates do not arrive every 10 ms (variable intervals), how would you modify the implementation? Assume you can obtain timestamps (e.g., via a system call like now_ms()) for each update.

Implement a multi-button click detector

Quick Overview

Comments (0)