Recursive procedure:

• Resolve an “empty” node by:

  • Check if the sibling is a 3-node.
    • Redistribute the siblings and parent’s items.
    • Re-adopt subrees appropriately.
  • If the sibling is a 2-node:
    • Merge the empty node with its sibling by moving an item from the parent node down to a sibling and moving the child of the empty node over to the sibling.
    • This can cause the parent node to become empty.