expeditaet/solutions/typescript/2020/23/src/p2.ts

Advent of Code Solutions

import { task } from '@alexaegis/advent-of-code-lib';
import {
	CircularLinkedList,
	CircularLinkedListNode,
} from '@alexaegis/advent-of-code-lib/linked-list';
import { max, min } from '@alexaegis/advent-of-code-lib/math';
import packageJson from '../package.json';

export const p2 = (input: string): number => {
	const circle = [...input].map((s) => Number.parseInt(s, 10));
	let high = circle.reduce(max);
	const low = circle.reduce(min);

	let nextLabel = high + 1;
	while (circle.length !== 1_000_000) {
		circle.push(nextLabel);
		nextLabel++;
	}
	high = circle.reduce(max);
	const ll = new CircularLinkedList<number>(circle);

	let cursor = ll.head;

	const m = new Map<number, CircularLinkedListNode<number>>();
	for (const link of cursor.forward()) {
		m.set(link.value, link);
	}

	for (let i = 0; i < 10_000_000; i++) {
		// pick up three cups
		const front = cursor.next;
		cursor.next = front.next.next.next;

		// select destination
		let destination: CircularLinkedListNode<number> | undefined;
		let val = cursor.value;
		let sub = 1;
		while (
			!destination ||
			destination === front ||
			destination === front.next ||
			destination === front.next.next
		) {
			destination = m.get(val - sub);
			sub++;
			if (val - sub < low) {
				sub = 0;
				val = high;
			}
		}

		// reinsert at destination
		const after = destination.next;
		destination.next = front;
		front.prev = destination;

		after.prev = front.next.next.next;
		front.next.next.next = after;

		// next
		cursor = cursor.next;
	}

	// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
	const cup = m.get(1)!;
	return cup.next.value * cup.next.next.value;
};

await task(p2, packageJson.aoc); // 286194102744 ~3717.03ms