part2.ts

import * as fs from 'fs';
const input = fs
	.readFileSync('input', 'utf8')
	.split('\n')
	.map((x) => x.split('').map((y) => Number(y)));

const rows = input.length;
const columns = input[0].length;
const graph = {};

for (let x = 0; x < columns; x++) {
	for (let y = 0; y < rows; y++) {
		const horizontal = (graph[`horizontal(${x},${y})`] = {
			heat: Infinity,
			neighbors: {},
		});
		const vertical = (graph[`vertical(${x},${y})`] = {
			heat: Infinity,
			neighbors: {},
		});
		for (let i = 4; i <= 10; i++) {
			if (x + i < columns)
				horizontal.neighbors[`vertical(${x + i},${y})`] = Array(i)
					.fill(0)
					.reduce((a, _, j) => a + input[y][x + j + 1], 0);
			if (x - i >= 0)
				horizontal.neighbors[`vertical(${x - i},${y})`] = Array(i)
					.fill(0)
					.reduce((a, _, j) => a + input[y][x - j - 1], 0);
			if (y + i < rows)
				vertical.neighbors[`horizontal(${x},${y + i})`] = Array(i)
					.fill(0)
					.reduce((a, _, j) => a + input[y + j + 1][x], 0);
			if (y - i >= 0)
				vertical.neighbors[`horizontal(${x},${y - i})`] = Array(i)
					.fill(0)
					.reduce((a, _, j) => a + input[y - j - 1][x], 0);
		}
	}
}

let result = Infinity;

const startingNeighbors = {
	...graph['horizontal(0,0)'].neighbors,
	...graph['vertical(0,0)'].neighbors,
};
for (const startingNeighbor of Object.keys(startingNeighbors)) {
	walk(startingNeighbor, startingNeighbors[startingNeighbor]);
}

function walk(neighbor, heat) {
	if (heat >= Math.min(graph[neighbor].heat, result)) return;
	if (neighbor.split('l')[1] === `(${columns - 1},${rows - 1})`) {
		result = heat;
		return;
	}
	graph[neighbor].heat = heat;
	const neighbors = Object.keys(graph[neighbor].neighbors);
	for (const key of neighbors) {
		walk(key, heat + graph[neighbor].neighbors[key]);
	}
}

console.log(result);