adventofcode/2022/11/part1.js

import * as R from "remeda";

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

function parseMonkey(block) {
  const re = new RegExp(
    `Starting items: (?<items>.+)
  Operation: new = (?<operation>.+)
  Test: divisible by (?<divisible>\\d+)
    If true: throw to monkey (?<ifTrue>\\d+)
    If false: throw to monkey (?<ifFalse>\\d+)`,
    "s"
  );

  const groups = { ...block.match(re).groups };

  ["divisible", "ifTrue", "ifFalse"].forEach(
    (k) => (groups[k] = parseInt(groups[k]))
  );

  groups.operation = eval("(old) => " + groups.operation);

  groups.items = groups.items.split(", ").map((x) => parseInt(x));

  return { ...groups, inspections: 0 };
}

const readInput = (...args) =>
  R.pipe(
    readFile(...args),
    (lines) => lines.split("\n\n"),
    R.compact, // remove last line
    R.map(parseMonkey)
  );

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

const playTurn = (monkeys, monkey) => {
  monkey.inspections += monkey.items.length;

  monkey.items = monkey.items.map((i) => monkey.operation(i));

  monkey.items = monkey.items.map((i) => Math.floor(i / 3));

  monkey.items.forEach((i) => {
    monkeys[i % monkey.divisible ? monkey.ifFalse : monkey.ifTrue].items.push(
      i
    );
  });

  monkey.items = [];

  return;
};

const playRound = (monkeys) => {
  monkeys.forEach((monkey) => playTurn(monkeys, monkey));
  return monkeys;
};

export default R.createPipe(
  R.clone,
  (monkeys) => R.times(20, () => playRound(monkeys)),
  R.last(),
  R.map(R.prop("inspections")),
  R.sortBy(R.identity),
  R.reverse,
  R.take(2),
  R.reduce((a, b) => a * b, 1)
);