part2.ts

import * as fs from 'fs';

const input = fs.readFileSync('input', 'utf8').split('\n');

let connections = input.map((line) => line.split('-'));

const pairMap = new Map<string, string[]>();
connections.forEach((connection) => {
	const [c1, c2] = connection;
	pairMap.set(c1, [...(pairMap.get(c1) ?? []), c2]);
	pairMap.set(c2, [...(pairMap.get(c2) ?? []), c1]);
});

const mergeConnection = (connections: string[][]) => {
	// Flatten the connections to find all computers connected to each computer in the group
	let groups = connections.flatMap((computers) => {
		let connectedComputers = computers.map((c) => pairMap.get(c));
		// Identify all computers that are interconnected within the group
		let addedComputers = connectedComputers.reduce((a, b) =>
			a.filter((value) => b.includes(value)),
		);
		// Create new groups by adding the interconnected computers to the existing group
		return [...addedComputers].map((addition) => [...computers, addition]);
	});
	// Generate unique group keys by sorting and joining the computer names
	const groupKeys = groups.map((group) => group.sort().join(','));
	// Return unique groups as arrays of computer names
	return [...new Set(groupKeys)].map((groupKey) => groupKey.split(','));
};

while (connections.length > 1) {
	connections = mergeConnection(connections);
}

console.log(connections[0].sort().join(','));