expeditaet/solutions/typescript/2019/19/src/p2.ts

Advent of Code Solutions

import { task } from '@alexaegis/advent-of-code-lib';
import packageJson from '../package.json';
import { hasBeam } from './p1.js';
import { parse } from './parse.js';

export const p2 = (input: string): number => {
	const tape = parse(input);
	const targetSide = 100 - 1;
	let prevX = 0;
	for (let y = targetSide + 1; y < 5000; y++) {
		let startedTrackingAt: number | undefined;
		let x = prevX;
		while (startedTrackingAt === undefined) {
			if (hasBeam(tape, x, y)) {
				startedTrackingAt = x;
				prevX = x;
			} else {
				x++;
			}
		}

		if (hasBeam(tape, x + targetSide, y - targetSide)) {
			return x * 10_000 + y - targetSide;
		}
	}

	return 0;
};

await task(p2, packageJson.aoc); // 17302065 ~905ms