floyd-rivest

A typescript implementation of the Floyd-Rivest selection algorithm.

This module exports a single function, select<T>(array: T[], k: number, compare?: (a: T, b: T) => number) => T implementing the Floyd-Rivest selection algorithm. select returns the k-smallest element of the input array, and mutates the array to ensure that the k-smallest element is at index k-1, all items at indices < (k-1) are less than or equal to array[k-1] and all items at indices > (k-1) are greater than or equal to array[k-1]. Elements are not sorted within each partition.

Usage

const { select } = require('floyd-rivest');
const array = [1,6,2,3,9,4,7,2,7,0,5];
const e = select(array, 3); // e = 2, the third-smallest element of the array
const ksmallest = array.slice(0,3); // ksmallest contains [0, 1, 2], not necessarily in that order