Graphshard70 minMobile Engineer

Feed Dependency DAG Recovery

Mobile Engineer signal: topological sort + cycle detection in a mobile feed ranking context. This is a ProdMatch-owned mobile engineer drill, framed as a March 2026 Dream11 Consumer Mobile simulation, not a copied platform question.

Company context

Dream11 · Consumer Mobile

Freshness

March 2026

Product surface

mobile feed ranking

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

Question

You own mobile feed ranking for a Mobile Engineer loop. Given cards and directed dependencies between them, return a valid execution order. If a cycle exists, return an empty list and identify that the rollout is blocked.

Input

n nodes labelled 0..n-1 and dependency pairs [before, after].

Output

A valid order of all nodes, or [] when dependencies contain a cycle.

Constraints

1 <= n <= 200000
0 <= dependencies.length <= 400000
The graph may be disconnected.

Concepts

offline sync
local cache
gesture streams
topological sort
cycle detection
dependency graph

cards: 4, deps: [[0,1],[0,2],[2,3]] -> [0,1,2,3] or [0,2,1,3]

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?

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Common Mistakes

Mark visited when enqueueing, not after repeated dequeue.
Do not ignore disconnected components if the product surface can have them.

Next Similar Problems

Sync Dependency DAG Recoverymedium Sync Evidence Path Finderhard Feed Evidence Path Findermedium