aoc23-18.mts

import { Advent, f, fm, chr, ord, arr } from "advent";
import { Set, Map } from "immutable";

const { compute, computeCheck } = await Advent({ day: 18 });

compute(2, async (input) => {
	const data = input.parse(f.nl((s) => {
		const [dir, dist, color] = s.split(" ");
		// return { dir, dist: parseInt(dist), color };
		return {
			dist: parseInt(color.slice(2, 7), 16),
			dir: (
				color[7] === "0" ? "R" :
				color[7] === "1" ? "D" :
				color[7] === "2" ? "L" :
				"U"
			),
		}
	}));

	let x = 0;
	let y = 0;
	let area = 0; // note: the value of this variable is actually _double_ the area
	let perimeter = 0;

	for (const { dir, dist } of data) {
		const x1 = x;
		const y1 = y;
		switch (dir) {
			case "R": x += dist; break;
			case "D": y += dist; break;
			case "L": x -= dist; break;
			case "U": y -= dist; break;
		}
		area += x1 * y - x * y1;
		perimeter += dist;
	}

	console.log(perimeter);
	return Math.abs(area / 2) + perimeter / 2 + 1;

	// leftovers from part 1...
	const grid: (string | undefined)[][] = arr(1000, () => arr(1000, () => undefined));
	let i = 500;
	let j = 500;

	for (const { dir, dist, color } of data) {
		for (let k = 0; k < dist; k++) {
			switch (dir) {
				case "R": j++; break;
				case "D": i++; break;
				case "L": j--; break;
				case "U": i--; break;
			}
			grid[i][j] = color;
		}
	}

	let visited = Set<string>();
	let queue: [number, number][] = [[0, 0]];

	while (queue.length > 0) {
		let [i, j] = queue.shift()!;
		if (i < 0 || i >= grid.length || j < 0 || j >= grid[i].length) {
			continue;
		}
		if (grid[i][j] !== undefined) {
			continue;
		}
		const loc = `${i},${j}`;
		if (visited.has(loc)) {
			continue;
		}
		visited = visited.add(loc);
		queue.push([i + 1, j]);
		queue.push([i - 1, j]);
		queue.push([i, j + 1]);
		queue.push([i, j - 1]);
	}

	return grid.length * grid[0].length - visited.size;
});