Data Structures and Algorithms in Java[1].pdf - Fulvio Frisone

These methods for adding and removing objects in an array of high scores are
simple. Nevertheless, they form the basis of techniques that are used repeatedly to
build more sophisticated data structures. These other structures may be more
general than the array structure above, of course, and often they will have a lot
more operations that they can perform than just add and remove. But studying
the concrete array data structure, as we are doing now, is a great starting point to
understanding these other structures, since every data structure has to be
implemented using concrete means.
In fact, later in this book, we will study a Java Collections Class, ArrayList,
which is more general than the array structure we are studying here. The
ArrayList has methods to do a lot of the things we will want to do with an
array, while also eliminating the error that occurs when adding an object to a full
array. The ArrayList eliminates this error by automatically copying the objects
into a larger array if necessary. Rather than discuss this process here, however, we
will say more about how this is done when we discuss the ArrayList in detail.
3.1.2 Sorting an Array
In the previous section, we worked hard to show how we can add or remove objects
at a certain index i in an array while keeping the previous order of the objects intact.
In this section, we study a way of starting with an array with objects that are out of
order and putting them in order. This is known as the sorting problem.
A Simple Insertion-Sort Algorithm
We study several sorting algorithms in this book, most of which appear in Chapter
11. As a warm up, we describe in this section a nice, simple sorting algorithm
called insertion–sort. In this case, we describe a specific version of the algorithm
where the input is an array of comparable elements. We consider more general
kinds of sorting algorithms later in this book.
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