adventofcode/2022/08/part2.js

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

import { outOfBound } from "./part1";

const V = (...args) => new Victor(...args);

function visibility(forest, x, y, dx, dy) {
  const pos = V(x, y);
  const inc = V(dx, dy);

  let vis = 0;

  while (true) {
    pos.add(inc);
    if (outOfBound(forest.length)(pos)) return vis;

    if (forest[x][y] <= forest[pos.x][pos.y]) return 1 + vis;
    vis++;
  }
}

const visibilityAround = (forest) => (x, y) =>
  [
    [0, 1],
    [0, -1],
    [1, 0],
    [-1, 0],
  ]
    .map((d) => visibility(forest, x, y, ...d))
    .reduce((a, b) => a * b);

export default R.createPipe(
  (forest) => {
    const va = visibilityAround(forest);
    return forest.map((l, x) => l.map((_, y) => va(x, y)));
  },
  R.flatten,
  R.maxBy(R.identity)
);