Graphshard70 minSecurity Engineer

Patch Dependency DAG Recovery

Security Engineer signal: topological sort + cycle detection in a patch priority queue context. This is a ProdMatch-owned security engineer drill, framed as a May 2026 PayPal Vulnerability Management simulation, not a copied platform question.

Company context

PayPal · Vulnerability Management

Freshness

May 2026

Product surface

patch priority queue

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

Question

You own patch priority queue for a Security Engineer loop. Given CVEs 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

attack graphs
policy tries
anomaly detection
topological sort
cycle detection
dependency graph

CVEs: 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?

Your rating tunes when this problem shows up again.

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

Attack Dependency DAG Recoverymedium Attack Evidence Path Finderhard Policy Dependency DAG Recoveryhard