part2.ts

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

const seeds = input[0]
	.split(': ')[1]
	.split(' ')
	.map((x) => Number(x))
	.reduce((a, x, i) => {
		if (i % 2 == 0) a.push([]);
		return a[a.length - 1].push(x), a;
	}, []);
const maps = input.slice(2).map((x) => x.split(' ').map((y) => Number(y)));
const results = [];

function expand(index, values) {
	if (index === maps.length) return [values];

	const result = [];
	const [destination, source, range] = maps[index];

	let nextMapIndex = index + 1;
	for (; nextMapIndex < maps.length && maps[nextMapIndex].length === 3; nextMapIndex++);

	if (
		values[0] < source &&
		values[0] + values[1] > source &&
		values[0] + values[1] <= source + range
	) {
		// tail part within a map
		const firstTuple = [values[0], source - values[0]];
		const lastTuple = [destination, values[1] - source + values[0]];
		// console.log('last part of ' + values + ' mapped to ' + lastTuple, destination, source, range, index, nextIndex);
		result.push(...expand(nextMapIndex, lastTuple), ...expand(index, firstTuple));
	} else if (
		values[0] >= source &&
		values[0] < source + range &&
		values[0] + values[1] > source + range
	) {
		// front part within a map
		const firstTuple = [destination + values[0] - source, source + range - values[0]];
		const lastTuple = [source + range, values[0] + values[1] - source - range];
		// console.log('first part of ' + values + ' mapped to ' + firstTuple, destination, source, range, index, nextIndex);
		result.push(...expand(nextMapIndex, firstTuple), ...expand(index, lastTuple));
	} else if (values[0] >= source && values[0] + values[1] <= source + range) {
		// whole part within a map
		// console.log('first part of ' + values + ' mapped to ' + [destination + values[0] - source, values[1]], destination, source, range, index, nextIndex);
		result.push(...expand(nextMapIndex, [destination + values[0] - source, values[1]]));
	} else if (values[0] < source && values[0] + values[1] > source + range) {
		// whole part cover a map
		const firstTuple = [values[0], source - values[0]];
		const middleTuple = [destination, range];
		const lastTuple = [source + range, values[0] + values[1] - source - range];
		// console.log('middle part of ' + values + ' mapped to ' + [destination, range], destination, source, range, index, nextIndex);
		result.push(
			...expand(index, lastTuple),
			...expand(nextMapIndex, middleTuple),
			...expand(index, firstTuple),
		);
	}

	if (result.length === 0) result.push(...expand(index + 1, values));
	return result;
}

for (const seed of seeds) {
	results.push(expand(0, seed));
}

console.log(results);
console.log(Math.min(...results.flat().map((x) => x[0])));