Insertion
To insert key v, search for the leaf where v should appear
If there’s space on the leave, insert the record
If no, split the leaf in half, and split the key range in its parent to point to the two leaves
- split the parent’s range [0, 19) to [0, 15) and [15, 19)
- if the parent was full, you’d split that too (not shown here)
- this automatically keeps the tree balanced