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

Given two sorted lists of event dicts (each with 'timestamp' and 'value') and a numeric tolerance, for each event in stream_a find the nearest event in stream_b whose |timestamp_a - timestamp_b| <= tolerance. If such a match exists, append a dict with keys 'a_value' (the A event's value), 'b_value' (the matched B event's value), and 'gap' (the absolute time difference, a float). Events with no B event inside the tolerance window are skipped. Return the list of match dicts in input-order of stream_a. If multiple stream_b events tie for nearest, choose the earliest. A single B event may match multiple A events (B events are never consumed).

Summary

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

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