Heap / Priority Queuehard70 minMobile Engineer

Sync Real-Time Top-K Prioritizer

Mobile Engineer signal: heap + top-k in a offline sync context. This is a ProdMatch-owned mobile engineer drill, framed as a May 2026 PolicyBazaar Mobile Platform simulation, not a copied platform question.

Company context

PolicyBazaar · 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

Your Mobile Platform team needs a live top-k view for mutations. Each update changes an item's score. Return the current top k item IDs after each update, ordered by score desc then ID asc.

Input

Initial scores, k, and update stream [id, delta].

Output

Top-k IDs after every update.

Constraints

1 <= items <= 200000
1 <= updates <= 200000
Scores can be negative.

Concepts

offline sync
local cache
gesture streams
heap
top-k
streaming rank

scores: [5,1,3], k=2, update [1,+5] -> [1,0]

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

Use a stable tie-breaker for equal scores.
Do not sort the full stream when k is small.

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