Graphsmedium45 minFrontend Engineer

Timeline Dependency DAG Recovery

Frontend Engineer signal: topological sort + cycle detection in a social timeline context. This is a ProdMatch-owned frontend engineer drill, framed as a March 2026 ServiceNow Consumer Web simulation, not a copied platform question.

Company context

ServiceNow · Consumer Web

Freshness

March 2026

Product surface

social timeline

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

Question

You own social timeline for a Frontend 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

render scheduling
state graphs
virtualization
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

Timeline Evidence Path Finderhard Autocomplete Dependency DAG Recoveryhard Autocomplete Evidence Path Findermedium