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LinkedIn·Machine Learning Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say
Apr 2026

Summary

LinkedIn ML Engineer interview with a from-scratch K-Means implementation question. The depth they expected on stopping criteria and edge cases was a bit more than I anticipated going in.

Questions Asked (1)

Q1

Implement K-Means clustering from scratch, including the fit API that takes a matrix of points and a number of clusters, returning final centroids and per-point cluster assignments.

Algorithms & Data StructuresTechnical Trade-offsSystem Design
Author's notes

I got the core loop down fine: initialize centroids, assign points by nearest Euclidean distance, recompute means, repeat.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem and assumptions (e.g., Euclidean distance, random initialization). Then outline the K-Means algorithm steps and implement the fit method with proper initialization, iterative assignment and update, and convergence check. Finally, discuss trade-offs and potential improvements.

Pro tip: Mention that you would use K-Means++ initialization to improve convergence and avoid poor local minima, and discuss how to handle empty clusters by reassigning them to the farthest points.

1. Clarify requirements and assumptions

Confirm the distance metric (typically Euclidean), initialization method, convergence criteria, and whether to return inertia or other metrics. Also discuss input data types and scalability considerations.

2. Initialize centroids

Choose an initialization strategy: random selection from data points or K-Means++ for better convergence. Explain the trade-offs and why K-Means++ is often preferred.

3. Implement assignment and update steps

Iteratively assign each point to the nearest centroid, then recompute centroids as the mean of assigned points. Handle edge cases like empty clusters by reassigning them to the farthest points from their centroids.

4. Define convergence and stopping criteria

Stop when centroid assignments no longer change or when the change in centroid positions falls below a tolerance. Also consider a maximum number of iterations to prevent infinite loops.

5. Return results and discuss trade-offs

Return final centroids and cluster assignments. Discuss computational complexity (O(n*k*d*i)), scalability, and potential improvements like Mini-Batch K-Means for large datasets.

Key Points to Mention

  • Choice of distance metric (Euclidean) and its implications
  • Initialization methods: random vs. K-Means++ and their impact on convergence
  • Handling empty clusters by reassigning to farthest points
  • Convergence criteria: assignment stability or centroid movement threshold
  • Computational complexity and scalability considerations
  • Potential improvements: Mini-Batch K-Means, elbow method for choosing k

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