# Mathematical Preliminaries

This chapter presents mathematical notation, background, and techniques used throughout the book. This material is provided primarily for review and reference. You might wish to return to the relevant sections when you encounter unfamiliar notation or mathematical techniques in later chapters.

Section 2.7 on estimation might be unfamiliar to many readers. Estimation is not a mathematical technique, but rather a general engineering skill. It is enormously useful to computer scientists doing design work, because any proposed solution whose estimated resource requirements fall well outside the problem’s resource constraints can be discarded immediately, allowing time for greater analysis of more promising solutions.

2.1 Sets and Relations

The concept of a set in the mathematical sense has wide application in computer science. The notations and techniques of set theory are commonly used when describing and implementing algorithms because the abstractions associated with sets often help to clarify and simplify algorithm design.

A set is a collection of distinguishable members or elements. The members are typically drawn from some larger population known as the base type. Each member of a set is either a primitive element of the base type or is a set itself. There is no concept of duplication in a set. Each value from the base type is either in the set or not in the set. For example, a set named P might consist of the three integers 7, 11, and 42. In this case, P’s members are 7, 11, and 42, and the base type is integer.

Figure 2.1 shows the symbols commonly used to express sets and their relationships. Here are some examples of this notation in use. First define two sets, P and Q.

P = {2,3,5}, Q = {5,10}.                               