Arrays and Stacks

Arrays

Arrays are data structures that allow storage of and random access to multiple elements

To access a given element, use its index number, starting from 0.

Examples of Array Usage and random data access

The string type, for example, is simply an array of character values.

The word data, placed into a string variable called word, is an array which looks like this:

• index 0: d
• index 1: a
• index 2: t
• index 3: a

To access the t, for instance, you can use word[2]

Stacks

A stack allows data to be inserted and removed at only one end, called the top.

Stack Data Management

To manage data in stacks, the following functions are generally needed:

• Push: Adds an item to the top of the stack
• pop: Removes the most recently added item off of the top of the stack
• empty: Checks if the stack is empty
• peek: Checks the item on top of the stack

String representation in a stack

Unlike arrays, stacks do not allow random access to data. Stacks are a last in, first out (LIFO) data structure.

To put the word data into a stack, the following operations must be preformed:

• push d
• push a
• push t
• push a

Once the data is in the stack, in order to access a given letter, you must continue to pop elements off the stack until the stack's top is equal to your target letter.

After each push or pop, you can use peek to check the current value of top

Interactive Demonstration

Feel free to enter various strings, which will be reversed using array iteration and stack push and pop methods

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