This book discusses the development and implementation of data structures and algorithms using VB.NET. The data structures we use here are found in the.NET Framework class library System.Collections. In this chapter we develop the concept of a collection by first discussing the implementation of our own collection class (using the array as the basis of our implementation) and then by covering the collection classes in the.NET Framework.

COLLECTIONS DEFINED

A collection is a structured data type that stores data and provides operations for adding data to the collection, removing data from the collection, updating data in the collection, and setting and returning the values of different attributes of the collection.

Collections can be broken down into two types—linear and nonlinear. A linear collection is a list of elements where one element follows the previous element. Elements in a linear collection are normally ordered by position (first, second, third, etc.). In the real world, a grocery list exemplifies a linear collection; in the computer world (which is also real), an array is designed as a linear collection.

Nonlinear collections hold elements that do not have positional order within the collection. An organizational chart is an example of a nonlinear collection, as is a rack of billiard balls. In the computer world, trees, heaps, graphs, and sets are nonlinear collections.

Collections, be they linear or nonlinear, have a defined set of properties that describe them and operations that can be performed on them.