Fixed-Radius Near Neighbor Algorithm

The fixed-radius near neighbor is a O(n + k) algorithm, where k is the number of pairs to get reported. Note that if k < n² then this algorithm should perform better than the naive O(n²) approach.

Further Reading:

• "The complexity of finding fixed-radius near neighbors" by JL Bentley, DF Stanat, and EH Williams
• Lecture 1 of Computational Geometry by D Mount for the proof of the runtime and a more intuitive read