Array Implementation of Stacks (Part 1)

Summary

The video introduces how to represent a stack using an array. A stack follows the last in, first out (LIFO) principle: the most recently added item is the first one removed.

Array Representation

• Store stack elements in consecutive positions of an array.
• Track the top element with an integer variable, top.
• When the stack is empty, set top to −1, indicating that no array position contains a stack element.
• Although an array supports access by index, stack operations work only at the top.

Push Operation

To add an element:

1. Check that the stack has room for another element.
2. Increment top.
3. Store the new element at array[top].

The new item becomes the topmost element.

Pop Operation

To remove an element:

1. Check that the stack is not empty (top must not be −1).
2. Read or remove the element at array[top].
3. Decrement top.

After the operation, the item below the removed one becomes the top.

Speakers and Sources

• Speaker: One instructor or narrator explains the material. The subtitles do not reliably identify the instructor by name.
• Source: Neso Academy