adventofcode/2022/16/part2.js

import { bidirectional } from "graphology-shortest-path";
import * as R from "remeda";
import u from "updeep";

import { buildGraph } from "./part1.js";

const findMaxSteam = (
  tunnels,
  graph,
  minutesLeft,
  unopened,
  opened,
  activeSteam,
  peeps
) => {
  console.log({ unopened, activeSteam, minutesLeft });

  let next = R.sortBy(peeps, R.prop("eta"));

  if (next[0].eta > minutesLeft) {
    return minutesLeft * activeSteam;
  }

  const delta = next[0].eta;
  const location = next[0].destination;

  const base = delta * activeSteam;
  minutesLeft -= delta;

  activeSteam += tunnels[next[0].destination].flow;
  opened = [...opened, next[0].destination];

  next = u.updateIn("1.eta", (eta) => eta - delta, next);

  const scores = [];

  let nothing = true;
  for (const destination of unopened) {
    const path = bidirectional(graph, location, destination);

    if (path.length > minutesLeft) {
      continue;
    }
    nothing = false;

    next = u.updateIn(
      "0",
      {
        location,
        eta: path.length,
        destination,
      },
      next
    );

    scores.push(
      findMaxSteam(
        tunnels,
        graph,
        minutesLeft,
        unopened.filter((x) => x !== destination),
        opened,
        activeSteam,
        next
      )
    );
  }

  if (nothing) {
    next = u.updateIn(
      "0",
      {
        location,
        eta: 999,
        destination: "END",
      },
      next
    );

    scores.push(
      findMaxSteam(
        tunnels,
        graph,
        minutesLeft,
        unopened,
        opened,
        activeSteam,
        next
      )
    );
  }

  return base + Math.max(...scores);
};

export default (tunnels) => {
  const possibilities = Object.keys(tunnels).filter((k) => tunnels[k].flow);

  const graph = buildGraph(tunnels);

  return findMaxSteam(tunnels, graph, 26, possibilities, [], 0, [
    { destination: "AA", eta: 0 },
    { destination: "AA", eta: 0 },
  ]);
};