day22-pt1

const deck1 = [
  14,
  23,
  6,
  16,
  46,
  24,
  13,
  25,
  17,
  4,
  31,
  7,
  1,
  47,
  15,
  9,
  50,
  3,
  30,
  37,
  43,
  10,
  28,
  33,
  32,
];

const deck2 = [
  29,
  49,
  11,
  42,
  35,
  18,
  39,
  40,
  36,
  19,
  48,
  22,
  2,
  20,
  26,
  8,
  12,
  44,
  45,
  21,
  38,
  41,
  34,
  5,
  27,
];

while (deck1.length && deck2.length) {
  const card1 = deck1.shift();
  const card2 = deck2.shift();

  if (card1 > card2) {
    deck1.push(card1, card2);
  } else {
    deck2.push(card2, card1);
  }
}

const winner = [...deck1, ...deck2];

console.log(
  winner.reduce((acc, curr, idx) => acc + curr * (winner.length - idx), 0)
);

day22-pt2

let deck1 = [
  14,
  23,
  6,
  16,
  46,
  24,
  13,
  25,
  17,
  4,
  31,
  7,
  1,
  47,
  15,
  9,
  50,
  3,
  30,
  37,
  43,
  10,
  28,
  33,
  32,
];

let deck2 = [
  29,
  49,
  11,
  42,
  35,
  18,
  39,
  40,
  36,
  19,
  48,
  22,
  2,
  20,
  26,
  8,
  12,
  44,
  45,
  21,
  38,
  41,
  34,
  5,
  27,
];

function recursiveCombat(d1, d2) {
  const played = {};
  while (d1.length && d2.length) {
    let hash = `${d1.join("-")}-${d2.join("-")}`;
    if (played[hash]) {
      // player 1 wins
      return [d1, []];
    } else {
      played[hash] = true;
    }

    if (deck1.length && deck2.length) {
      const card1 = d1.shift();
      const card2 = d2.shift();

      if (card1 <= d1.length && card2 <= d2.length) {
        const [subgameDeck1, subgameDeck2] = recursiveCombat(
          d1.slice(0, card1),
          d2.slice(0, card2)
        );

        if (subgameDeck1.length > subgameDeck2.length) {
          d1.push(card1, card2);
        } else if (subgameDeck2.length > subgameDeck1.length) {
          d2.push(card2, card1);
        }
      } else if (card1 > card2) {
        d1.push(card1, card2);
      } else {
        d2.push(card2, card1);
      }
    }
  }

  return [d1, d2];
}

[deck1, deck2] = recursiveCombat(deck1, deck2);

console.log(deck1, deck2);

const winner = [...deck1, ...deck2];

console.log(
  winner.reduce((acc, curr, idx) => acc + curr * (winner.length - idx), 0)
);