to select a whole subtree of a particular node of a tree.
u have to modify the tree representation in one of the two ways
(according to you fine-tuned needs)
(1) store in the EACH node the PATH from root to this node
(2) store (l,r) segment representing the INCLUSIONS of nodes into other
nodes subtree (exactly as segments include each other)
(2) i forgot the "official" name of this type of tree representation.
