Advent of Code 2022 - Day 13

advent-of-code-2022-13.js

const INPUT = `...`;

(function doPart1() {
  const pairs = INPUT.split(/\n\n/).map((p) =>
    p.split(/\n/).map((l) => eval(l))
  );
  const correctIndices = pairs
    .filter((p) => comparePackets(...p) < 0)
    .map((p) => pairs.indexOf(p) + 1);
  console.log(correctIndices.reduce((a, b) => a + b, 0));
})();

(function doPart2() {
  const DIVIDERS = [[[2]], [[6]]];
  let packets = INPUT.split(/\n/)
    .filter(Boolean)
    .map((p) => eval(p));
  packets.push(...DIVIDERS);
  packets.sort(comparePackets);
  console.log(
    DIVIDERS.map((d) => packets.indexOf(d) + 1).reduce((a, b) => a * b, 1)
  );
})();

function comparePackets(l, r) {
  if ([l, r].every((a) => !Array.isArray(a))) return l - r;
  [l, r] = [l, r].map((a) => (Array.isArray(a) ? a : [a]));
  for (let i = 0; i < Math.max(l.length, r.length); i++) {
    if (l[i] === undefined) return -1;
    if (r[i] === undefined) return 1;
    if (l[i] === r[i]) continue;
    const cmp = comparePackets(l[i], r[i]);
    if (cmp !== undefined) return cmp;
  }
}