part2.ts

import * as fs from 'fs';
const input = fs.readFileSync('input', 'utf8').split('\n\n')[0].split('\n');

const workflows = {};

for (const line of input) {
	const info = line.split('{');
	workflows[info[0]] = info[1]
		.slice(0, -1)
		.split(',')
		.map((x) => {
			if (x.includes('>')) {
				const [category, value] = x
					.split('>')
					.map((x, i) => (i == 1 ? Number(x.split(':')[0]) : 'xmas'.indexOf(x)));
				return [category, '>', value, x.split(':')[1]];
			} else if (x.includes('<')) {
				const [category, value] = x
					.split('<')
					.map((x, i) => (i == 1 ? Number(x.split(':')[0]) : 'xmas'.indexOf(x)));
				return [category, '<', value, x.split(':')[1]];
			} else return x;
		});
}

let result = 0;

const queue = [
	[
		'in',
		[
			[1, 4000],
			[1, 4000],
			[1, 4000],
			[1, 4000],
		],
	],
];
while (queue.length > 0) {
	const [workflow, intervals] = queue.pop();
	if (workflow == 'A' || workflow == 'R') {
		if (workflow == 'A') {
			result += intervals.reduce((a, b) => a * (b[1] - b[0] + 1), 1);
		}
		continue;
	}

	for (const [left, op, right, then] of workflows[workflow].slice(0, -1)) {
		const [low, high] = intervals[left];

		if ((op == '>' && right >= high) || (op == '<' && right <= low)) continue;
		if ((op == '>' && right < low) || (op == '<' && right > high)) {
			queue.push([then, intervals]);
			break;
		}

		intervals[left] = [op == '>' ? low : right, op == '>' ? right : high];
		const newIntervals = [...intervals];
		newIntervals[left] = [op == '>' ? right + 1 : low, op == '>' ? high : right - 1];
		queue.push([then, newIntervals]);
	}

	queue.push([workflows[workflow].slice(-1)[0], intervals]);
}

console.log(result);