# Question: Observe that whenever the size field of a node is

Observe that whenever the size field of a node is referenced in either OS-SELECT or OSRANK, it is used only to compute the rank of the node in the sub tree rooted at that node. Accordingly, suppose we store in each node its rank in the sub tree of which it is the root. Show how this information can be maintained during insertion and deletion. (Remember that these two operations can cause rotations.)

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