Definition A tree is a collection of nodes. The collection can be empty: otherwise, a tree consists of (1) a distinguished node r, called the root; (2)and zero or more nonempty(sub)trees T1,., Tk, each of whose roots are connected by a directed edge from r Note:
1. Introduction: Breaking the lgn Barrier 2. Rectangular Arrays 3. Tables of Various Shapes 4. Tables: A New Abstract Data Type 5. Application: Radix Sort