Advent-of-Code-2022/16/solution.mjs

import { readFileSync } from 'node:fs';

const input = readFileSync('input', 'utf-8');


const valves = new Map(input
  .split('\n')
  .filter(Boolean)
  .map(line => {
    const valve = line.match(/Valve (\w+)/)[1];
    const rate = parseInt(line.match(/rate=(\d+)/)[1]);
    const to = line.match(/valves? (.*)/)[1].split(', ');
    return [valve, {valve, rate, to}];
  })
);

function shortestPath(v, vDest, path=[]) {
  const valve = valves.get(v);

  if (valve.to.includes(vDest)) {
    return [...path, v, vDest];
  }
  return valve.to
    .filter(to => !path.includes(to))
    .map(to => shortestPath(to, vDest, [...path, v]))
    .filter(Boolean)
    .sort((p1, p2) => p1.length - p2.length)[0];
}

// Add a property to all valves containing links to all other valves with a
// flow rate greater than 0 and the time it will take to reach them
const valvesWithFlow = [...valves.values()]
  .filter(valve => valve.rate > 0);
for (const valve of valves.values()) {
  valve.usefulTo = valvesWithFlow
    .filter(vDest => vDest.valve !== valve.valve)
    .map(vDest => ({
      valve: vDest.valve,
      time: shortestPath(valve.valve, vDest.valve).length - 1,
      rate: vDest.rate
    }));
}

function product(...arrs) {
  if (!arrs.length) return [];
  return arrs.reduce((result, arr) =>
    result.flatMap(r =>
      arr.map(a => [...r, a])
    ),
    [[]]
  )
}

// General solution for n players
function solve(players, rate=0) {
  for (const player of players) {
    const valve = valves.get(player.path[player.path.length - 1]);

    if (valve.rate > 0 && !player.opened) {
      player.opened = true;
      player.timeRemaining -= 1;
      rate += valve.rate * Math.max(0, player.timeRemaining);
    }
  }

  // Array of valve names which haven't been visited
  const unvisitedValves = valvesWithFlow
    .map(v => v.valve)
    .filter(valve => !players.find(p => p.path.includes(valve)));

  // Exit conditions
  if (
    unvisitedValves.length === 0 ||
    players.every(player => player.timeRemaining <= 0)
  ) {
    return [rate, players];
  }

  // Decide who is moving
  const maxTimeRemaining = players.reduce(
    (max, player) => Math.max(max, player.timeRemaining),
    0
  );
  const movingPlayers = players.filter(
    player => player.timeRemaining === maxTimeRemaining
  );
  const nonMovingPlayers = players.filter(
    player => !movingPlayers.includes(player)
  );

  const playerMoves = product(...movingPlayers
    .map(player => {
      const valve = valves.get(player.path[player.path.length - 1]);
      const destinations = valve.usefulTo
        .filter(to => unvisitedValves.includes(to.valve))
        .filter((to, _, tos) => !tos.find((otherTo) =>
          otherTo.rate > to.rate &&
          otherTo.time <= to.time
        ));
      if (destinations.length < movingPlayers.length) {
        destinations.push(undefined);
      }
      return destinations;
    })
  ).filter(moves => {
    const valves = moves.filter(Boolean).map(to => to.valve);
    return (
      valves.length !== 0 &&
      new Set(valves).size === valves.length
    );
  });

  return playerMoves
    .map(moves => {
      const movedPlayers = moves.map((to, i) => {
        const player = movingPlayers[i];
        if (to === undefined) {
          // Not moving
          return player;
        }
        return {
          timeRemaining: player.timeRemaining - to.time,
          opened: false,
          path: [...player.path, to.valve]
        };
      });

      return solve([...nonMovingPlayers, ...movedPlayers], rate);
    })
    .filter(Boolean)
    .sort(([rate1], [rate2]) => rate2 - rate1)[0];
}


const solution1 = solve([{
  timeRemaining: 30,
  opened: false,
  path: ['AA']
}]);
console.log(`Max pressure released in 30 minutes: ${solution1[0]}`);

const solution2 = solve([{
  timeRemaining: 26,
  opened: false,
  path: ['AA']
}, {
  timeRemaining: 26,
  opened: false,
  path: ['AA']
}]);
console.log(`Max pressure released with elephant: ${solution2[0]}`);