DeleteAndInsert2.swift

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    if collectionView == baseCollectionView {
        let alphabetLetter = baseCollectionViewArray[indexPath.item]
        secondCollectionViewArray.append(alphabetLetter)
        let newIndexPath = IndexPath(item: secondCollectionViewArray.count - 1, section: 0)
        secondCollectionView.insertItems(at: [newIndexPath])

        baseCollectionViewArray.remove(at: indexPath.item)
        baseCollectionView.deleteItems(at: [indexPath])

    } else {
      ///ADD THIS STUFF
        let alphabetLetter = secondCollectionViewArray[indexPath.item]
        baseCollectionViewArray.insert(alphabetLetter, at: 0)
        let newIndexPath = IndexPath(item: 0, section: 0)
        ///I guess we'll put it at the front for now?
        baseCollectionView.insertItems(at: [newIndexPath])

        secondCollectionViewArray.remove(at: indexPath.item)
        secondCollectionView.deleteItems(at: [indexPath])
    }
}