Graphshard70 minSecurity Engineer

ACL Dependency DAG Recovery

Security Engineer signal: topological sort + cycle detection in a permission minimizer context. This is a ProdMatch-owned security engineer drill, framed as a April 2026 PhonePe Zero Trust simulation, not a copied platform question.

Company context

PhonePe · Zero Trust

Freshness

April 2026

Product surface

permission minimizer

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

Question

You own permission minimizer for a Security Engineer loop. Given grants 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

grants: 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