🔥 TOP 10 Priority - Most popular ML algorithm #6

Overview

Implement K-Nearest Neighbors (kNN) for classification, one of the most widely-used instance-based learning algorithms.

Implementation Details

• Distance metrics: Euclidean, Manhattan, Minkowski
• Weighted vs unweighted voting
• Efficient neighbor search (brute force initially, KD-tree later)
• Cross-validation for optimal k selection

References

• Instance-based learning algorithm
• Non-parametric method
• Simple yet effective baseline

Acceptance Criteria

• KNN struct with fit/predict
• Distance metric selection
• Weighted voting option
• Comprehensive tests (EXTREME TDD)
• Example: knn_iris.rs
• Book chapter: ml-fundamentals/knn.md

Priority Justification

kNN is #6 in industry usage per Analytics Vidhya 2025 ranking