122 lines
3.3 KiB
JavaScript
122 lines
3.3 KiB
JavaScript
import { readFileSync } from 'node:fs';
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const input = readFileSync('input', 'utf-8');
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const cubes = input
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.split('\n')
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.filter(line => !!line.trim())
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.map(coords => {
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const [x, y, z] = coords.split(',').map(n => parseInt(n));
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return {x, y, z};
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});
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const surfaceArea = cubes.map(cubeA => {
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const touchingCubes = cubes.filter(cubeB => {
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const xDiff = Math.abs(cubeA.x - cubeB.x);
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const yDiff = Math.abs(cubeA.y - cubeB.y);
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const zDiff = Math.abs(cubeA.z - cubeB.z);
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return (
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(xDiff === 1 && yDiff === 0 && zDiff === 0) ||
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(yDiff === 1 && zDiff === 0 && xDiff === 0) ||
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(zDiff === 1 && xDiff === 0 && yDiff === 0)
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);
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});
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const nonConnectedSides = 6 - touchingCubes.length;
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return nonConnectedSides;
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}).reduce((total, sides) => total + sides);
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console.log(`The surface area of the droplet is: ${surfaceArea}`);
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function minMax(dimension) {
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return [
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cubes.reduce((min, coords) => Math.min(min, coords[dimension]), Infinity),
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cubes.reduce((max, coords) => Math.max(max, coords[dimension]), -Infinity),
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];
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}
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function isCoordEqual(coordA, coordB) {
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return coordA.every((v, i) => coordB[i] === v);
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}
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function uniqueCoordsFilter(coordA, i, coords) {
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return coords.findLastIndex(coordB => isCoordEqual(coordA, coordB)) === i;
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}
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function getAllConnected(startX, startY, startZ, isConnected) {
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const connected = [];
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let toVisit = [[startX, startY, startZ]];
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while (true) {
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connected.push(...toVisit);
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toVisit = toVisit.flatMap(([x, y, z]) => [
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[x + 1, y, z ],
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[x - 1, y, z ],
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[x, y + 1, z ],
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[x, y - 1, z ],
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[x, y, z + 1],
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[x, y, z - 1]
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])
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.filter(coordA =>
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!connected.find(coordB => isCoordEqual(coordA, coordB))
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)
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.filter(uniqueCoordsFilter)
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.filter(([x, y, z]) => isConnected(x, y, z));
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if (!toVisit.length) {
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break;
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}
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}
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return connected;
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}
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const [minX, maxX] = minMax('x');
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const [minY, maxY] = minMax('y');
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const [minZ, maxZ] = minMax('z');
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// Get all coordinates external to droplet with a border of 2
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const connected = getAllConnected(minX - 2, minY - 2, minZ - 2, (x, y, z) => {
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return (
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x >= minX - 2 &&
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x <= maxX + 2 &&
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y >= minY - 2 &&
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y <= maxY + 2 &&
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z >= minZ - 2 &&
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z <= maxZ + 2 &&
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// Not part of the droplet
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!cubes.find(coord => coord.x === x && coord.y === y && coord.z === z)
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);
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});
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// Calculate internal surface area of inverted droplet
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const externalSurfaceArea = connected.map(([ax, ay, az]) => {
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// Skip coordinates right on the edge
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if (
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ax < minX - 1 || ax > maxX + 1 ||
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ay < minY - 1 || ay > maxY + 1 ||
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az < minZ - 1 || az > maxZ + 1
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) {
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return 0;
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}
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const touchingCubes = connected.filter(([bx, by, bz]) => {
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const xDiff = Math.abs(ax - bx);
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const yDiff = Math.abs(ay - by);
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const zDiff = Math.abs(az - bz);
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return (
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(xDiff === 1 && yDiff === 0 && zDiff === 0) ||
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(yDiff === 1 && zDiff === 0 && xDiff === 0) ||
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(zDiff === 1 && xDiff === 0 && yDiff === 0)
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);
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});
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const nonConnectedSides = 6 - touchingCubes.length;
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return nonConnectedSides;
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}).reduce((total, sides) => total + sides);
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console.log(
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`The EXTERNAL surface area of the droplet is: ${externalSurfaceArea}`
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);
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