adventofcode/2022/09/part1.js

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

import { readFile } from "../05/part1.js";
import { passthru } from "../08/part1.js";

const directions = {
  R: new Victor(1, 0),
  L: new Victor(-1, 0),
  U: new Victor(0, 1),
  D: new Victor(0, -1),
};

const parseLine = R.createPipe(
  (line) => line.split(" "),
  ([direction, times]) => Array(parseInt(times)).fill(directions[direction])
);

export const readInput = (...args) =>
  R.pipe(
    readFile(...args),
    (text) => text.split("\n"),
    R.compact,
    R.map(parseLine),
    R.flatten
  );

export const puzzleInput = readInput(import.meta.url, "input");
export const sample = readInput(import.meta.url, "sample");

export const touching = (v1, v2) =>
  [v1.distanceX(v2), v1.distanceY(v2)].every((x) => x * x <= 1);

export const moveOnce = (head, tail) => (d) => {
  head.add(d);

  if (touching(head, tail)) return tail.toString();

  const delta = head.clone().subtract(tail).normalize();

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

  tail.add(delta);

  return tail.toString();
};

const moveAround = (directives) => {
  const head = new Victor(0, 0);
  const tail = new Victor(0, 0);

  const move = moveOnce(head, tail);
  return directives.map(move);
};

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