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Arrays & Hashingeasy25 minMobile Engineer

Sync Duplicate Signal Resolver

Mobile Engineer signal: hash map + dedupe in a offline sync context. This is a ProdMatch-owned mobile engineer drill, framed as a May 2026 Salesforce Mobile Platform simulation, not a copied platform question.

Company context

Salesforce · Mobile Platform

Freshness

May 2026

Product surface

offline sync

ProdMatch interview simulation based on product-team patterns; not a claim of a real company question.

Question

For offline sync, collapse duplicate mutations by external ID. Keep the newest event per ID and return IDs in first-seen order.

Input

  • Array of events {id, version}.

Output

  • Deduped IDs and their kept version.

Constraints

  • 1 <= events.length <= 200000
  • Versions are comparable integers.

Concepts

  • offline sync
  • local cache
  • gesture streams
  • hash map
  • dedupe
  • stable ordering

[(a,1),(b,1),(a,3)] -> [(a,3),(b,1)]

Approach

Try framing your own approach first. The 30 seconds you think before peeking is where learning happens.

Clean Solution

Reveal the approach first.

How well did you understand?

Your rating tunes when this problem shows up again.

Common Mistakes

  • Do not sort if first-seen order is required.
  • Treat duplicate IDs with equal versions deterministically.

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