Chapter 3. Stacks

You learned in the previous chapter how to create and use arrays, which are the most common type of data structure in Computer Science. As you learned, we can add and remove elements from an array at any index desired. However, sometimes we need some form of data structure where we have more control over adding and removing items. There are two data structures that have some similarities to arrays but give us more control over the addition and removal of elements. These data structures are stacks and queues. In this chapter, we will cover stacks.

A stack is an ordered collection of items that follows the LIFO (short for Last In First Out) principle. The addition of new items or the removal of existing items takes place at the same end. The end of the stack is known as the top and the opposite is known as the base. The newest elements are near the top, and the oldest elements are near the base.

We have several examples of stacks in real life, for example, a pile...