Structures: What Next?

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Structures: What Next ?

Before we end our explanation of structures, we would like to mention one of the more important uses of structures: creating new data forms. Computer users have developed data forms much more efficient for certain problems than the arrays and simple structures we have presented. These forms have names such as queues, binary trees, heaps, hash tables, and graphs. Many such forms are built from linked structures. Typically, each structure contains one or two items of data plus one or two pointers to other structures of the same type. Those pointers link one structure to another and furnish a path to enable you to search through the overall tree of structures. For example, Figure 14.3 shows a binary tree structure, with each individual structure (or node) connected to the two below it.

Figure 14.3. A binary tree structure.

Is the hierarchical, or tree, structure shown in Figure 14.3 more efficient than an array? Consider the case of a tree with ten levels of nodes. It has 2 ¹⁰ “1, or 1,023, nodes in which you could store up to 1,023 words. If the words were arranged according to some sensible plan, you could start at the top level and find any word in ”at most ”nine moves as your search moved down one level to the next. If you had the words in an array, you might have to search all 1,023 elements before finding the word you sought.

If you are interested in more advanced concepts such as this, you can consult any number of computer science texts on data structures. With the C structures, you can create and use virtually every form presented in these texts . Also, Chapter 17, "Advanced Data Representation," investigates some of these advanced forms.

That's our final word on structures for this chapter, but we will present examples of linked structures in Chapter 17. Next, we'll look at two other C features for dealing with data: the union and typedef .

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