The Stream Joiner

A hard Python interview practice problem on DataDriven. Write and execute real python code with instant grading.

Domain

Python

Difficulty

hard

Seniority

L5

Problem

You're correlating two time-sorted event streams where each event is a dict carrying a `timestamp` and a `value`, given a numeric `tolerance`. Walking `stream_a` in order, pair each event with the single nearest event in `stream_b` whose timestamp lies within `tolerance` of it, emitting a dict of `a_value`, `b_value`, and the absolute `gap`; an A event with nothing inside its window contributes no row. When two B events are equally near, keep the earlier one, and remember a single B event can be the nearest match for several A events.

Summary

Events don't wait for each other. This does.

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