Implement k-means from scratch

Last updated: January 5, 2026

Quick Overview

Write a clean implementation of logistic regression without using ML libraries.

Brex
Machine Learning
Machine Learning Engineer
Brex
January 5, 2026
Machine Learning Engineer
Take-home Project
Machine Learning
Easy

175

6

1,110 solved


Write a clean implementation of logistic regression without using ML libraries.

Brex asks this during the Take-home Project to assess your depth in ML. They expect you to discuss the mathematical foundations, practical considerations, and common pitfalls when applying these techniques in production.

What the Interviewer Expects
  • Explain the concept clearly with intuitive examples
  • Discuss when and why to use this technique
  • Identify common pitfalls and how to avoid them
  • Compare with alternative approaches at a high level
Key Topics to Cover
Supervised vs unsupervised learning
Ensemble methods (bagging, boosting, stacking)
Class imbalance handling
Overfitting and underfitting
Cross-validation and model evaluation
Feature importance and selection
How to Approach This
  1. Understand the bias-variance trade-off. High training accuracy but low test accuracy signals overfitting.
  2. Choose evaluation metrics carefully based on the problem. Accuracy alone is often insufficient.
  3. Feature engineering is often more impactful than model selection.
  4. Know when to use tree-based models (tabular data) vs neural networks (unstructured data).
  5. Handle class imbalance with SMOTE, class weights, or appropriate loss functions.
Possible Follow-up Questions
  • How would you explain this model's predictions to a non-technical stakeholder?
  • How would you ensure reproducibility in your ML pipeline?
  • What are the computational costs of this approach at scale?
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Explore ML Interview Prep
Sample Answer
Core Concept: K-Means Clustering

K-means is an unsupervised learning algorithm designed to partition a dataset into K distinct clusters based on feature similarity. The core idea is to minimize the variance within each cluster while ...

How It Works: Algorithmic Steps

The K-means algorithm follows these steps:

  1. Initialization: Randomly select K data points as initial centroids.
  2. Assignment: Assign each data point to the nearest centroid based on Euc...

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