TAOCP 2.3 Exercise 9
In both binary trees of (1), the root is `A`.
Exercise 9. [**] [00] In the two binary trees of (1), which node is the root (B or A)?
Verified: no
Solve time: 34s
In both binary trees of (1), the root is A.
A binary tree is a tree in the sense of Section 2.3, with a distinguished node called the root. In the diagrams of (1), A is the unique node from which every other node descends, while B is a child of A. Hence A is the root and B is not. Therefore the answer is
$\boxed{A}$