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Netflix·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Phone screen for a Netflix SWE role, basically one coding problem the whole time. Graph stuff, topological sort. Pretty standard but the follow-ups can spiral if you're not careful.

Questions Asked (1)

Q1

Given N tasks and a list of dependency pairs (a, b) meaning a must complete before b, return any valid ordering of all tasks, or indicate that no valid ordering exists due to a cycle.

Algorithms & Data Structures
Author's notes

Classic topological sort.

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AI HintsAI Generated

Suggested Approach

Model the tasks and dependencies as a directed graph and use topological sorting (Kahn's algorithm or DFS) to find a valid ordering. If a cycle is detected, return an error indicating no valid ordering exists.

Pro tip: Discuss the trade-offs between Kahn's algorithm and DFS-based topological sort, and mention that Kahn's algorithm naturally detects cycles by checking if all nodes are processed.

1. Clarify the problem

Confirm that tasks are nodes and dependencies are directed edges. Ask if the graph is guaranteed to be a DAG or if cycles are possible.

2. Choose an algorithm

Select either Kahn's algorithm (BFS-based) or DFS-based topological sort. Explain your choice based on cycle detection and implementation simplicity.

3. Implement the algorithm

For Kahn's: compute in-degrees, use a queue, and process nodes. For DFS: perform depth-first search and track visited and recursion stack.

4. Detect cycles

If using Kahn's, check if the number of processed nodes equals N. If using DFS, check for back edges during traversal.

5. Return the result

If no cycle, return the topological order. If cycle, return an indication that no valid ordering exists.

Key Points to Mention

  • Topological sorting is only possible for Directed Acyclic Graphs (DAGs).
  • Kahn's algorithm uses in-degree and a queue; DFS uses recursion stack for cycle detection.
  • Time complexity is O(V+E) for both approaches.
  • Space complexity is O(V+E) for storing the graph and auxiliary data structures.
  • Cycle detection is crucial; without it, the algorithm may produce an invalid order.
  • Edge cases: empty graph, single node, disconnected components, self-loops.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.