AoC 2023 - Day 11 - JS

// Day 11 - year 2023
const input = require("fs").readFileSync("input.txt", "utf8").split("\n");

const is_empty_col = Array(input[0].length).fill(true);
const is_empty_row = Array(input.length).fill(true);

const galaxies = [];

input.forEach((row, y) => {
    row.split("").forEach((ch, x) => {
        if (ch === '#') {
            galaxies.push({ x, y });
            is_empty_col[x] = false;
            is_empty_row[y] = false;
        }
    });
});

const insert_cols = [];
const insert_rows = [];

is_empty_col.forEach((v, col) => { if (v) insert_cols.push(col) });
is_empty_row.forEach((v, row) => { if (v) insert_rows.push(row) });

console.log("part 1:", sum_distances(expand(galaxies, 1)));
console.log("part 2:", sum_distances(expand(galaxies, 999999)));

function expand(galaxies, displace) {
    for (galaxy of galaxies) {
        let displace_x = insert_cols.filter(v => v < galaxy.x).length;
        let displace_y = insert_rows.filter(v => v < galaxy.y).length;
        galaxy.x += displace_x * displace;
        galaxy.y += displace_y * displace;
    }
    return galaxies;
}

function sum_distances(galaxies) {
    let sum = 0;
    for (let i = 0; i < galaxies.length - 1; i++) {
        for (let j = i + 1; j < galaxies.length; j++) {
            let dist = Math.abs(galaxies[i].x - galaxies[j].x) + Math.abs(galaxies[i].y - galaxies[j].y);
            sum += dist;
        }
    }
    return sum;
}