adventofcode/2022/09/part2.js

import * as R from "remeda";
import Victor from "@a-robu/victor";

import { touching, readInput } from "./part1.js";

export const bigSample = readInput(import.meta.url, "bigSample");

export const moveOnce = (knots) => (d) => {
  R.first(knots).add(d);

  for (const i of R.range(1, knots.length)) {
    if (touching(knots[i - 1], knots[i])) break;

    const delta = knots[i - 1].clone().subtract(knots[i]).normalize();

    if (delta.x * delta.y) {
      delta.x = delta.x > 0 ? 1 : -1;
      delta.y = delta.y > 0 ? 1 : -1;
    }

    knots[i].add(delta);
  }

  return R.last(knots).toString();
};

const moveAround = (directives) => {
  const knots = Array(10)
    .fill(null)
    .map(() => new Victor(0, 0));

  const move = moveOnce(knots);
  return directives.map(move);
};

export default R.createPipe(moveAround, R.uniq, (moves) => moves.length);