Sets and Maps

In the last chapter we studied sequences which are used to keep track of lists of things where duplicate values are allowed. For instance, there can be two sixes in a sequence or list of integers. In this chapter we look at sets where duplicate values are not allowed. After examining sets we’ll move on to talk about maps. Maps may also be called dictionaries or hash tables.The term hash table actually suggests an implementation of a set or map. The primary focus of this chapter is in understanding hashing. Hashing is a very important concept in Computer Science because it is a very efficient method of searching for a value. To begin the chapter we’ll motivate our interest in hashing, then we’ll develop a hashing algorithm for finding values in a set. We’ll also apply hashing to the building of sets and maps. Then we’ll look at an important technique that uses hashing called memoization and we’ll apply that technique to a couple of problems.