// https://www.freecodecamp.org/learn/coding-interview-prep/algorithms/inventory-update

function updateInventory(arr1, arr2) {
  const inventory = {};
  arr1.forEach(([quantity, item]) => {
    inventory[item] = quantity;
  });
  arr2.forEach(([quantity, item]) => {
    if (inventory[item]) {
      inventory[item] += quantity;
    } else {
      inventory[item] = quantity;
    }
  });
  const inventoryArr = [];
  for (const [item, quantity] of Object.entries(inventory)) {
    inventoryArr.push([quantity, item]);
  }
  inventoryArr.sort(([quantityA, itemA], [quantityB, itemB]) =>
    itemA > itemB ? 1 : -1
  );
  return inventoryArr;
}

console.log(
  updateInventory(
    [
      [21, "Bowling Ball"],
      [2, "Dirty Sock"],
      [1, "Hair Pin"],
      [5, "Microphone"],
    ],
    [
      [2, "Hair Pin"],
      [3, "Half-Eaten Apple"],
      [67, "Bowling Ball"],
      [7, "Toothpaste"],
    ]
  )
);