unique-pairs.js

/**
 * Unique sets in JavaScript
 *
 * Inspired by https://fosstodon.org/@[email protected]/109354031141521705
 *
 * Author: Timo Tijhof (2022).
 * License: Public domain.
 */

const NAMES = [
	'Apricot',
	'Banana',
	'Cherimoya',
	'Gac',
	'Irvingia',
	'Rambutan'
];

// Given 6 values in a circle, we can make 6 connections (or "pairs")
//
// A pair must be more than 0 but less than SIZE distance from each
// other to not be with itself. That means 1—5 distance in our case.
//
// This allows for SIZE-1 (5) sets of 6 pairs, or 30 unique pairs.
const POSSIBLE_SETS = NAMES.length - 1;

const all = new Set();

for (let distance = 1; distance <= POSSIBLE_SETS; distance++) {
	const current = new Set();
	for (let i = 0; i < NAMES.length; i++) {

		const a = NAMES[i];
		// mod is the same as deducting until you're under
		const b = NAMES[(i + distance) % NAMES.length];

		const pair = a + ' ' + b;
		current.add(pair);
		all.add(pair);
	}

	console.log(
		`d=${distance} Set(${current.size}) =`,
		Array.from(current).join(',\n') + '.\n'
	);
}

console.log('Unique pairs', all.size);