How do you implement a stack using an array?

You can implement a stack using an array by using push and pop operations to add and remove elements respectively.

A stack is a linear data structure that follows a particular order in which operations are performed. The order may be LIFO (Last In First Out) or FILO (First In Last Out). Mainly the following three basic operations are performed in the stack:

1. Push: Adds an element to the collection. A pointer called TOP is used to keep track of the top element in the stack.
2. Pop: Removes an element from the collection. The items are popped from the top of the stack.
3. Peek or Top: Returns the top element of the stack.
4. isEmpty: Returns true if the stack is empty, else false.

To implement a stack using an array, you would first need to initialise an array of a certain size. This size will be the maximum capacity of your stack. You will also need a variable (let's call it 'top') to keep track of the index of the topmost element in the stack. This variable will be initialised to -1, indicating that the stack is empty.

When you want to add (push) an element to the stack, you first check if the stack is full (i.e., if 'top' is equal to the maximum size of the array minus one). If it is not full, you increment 'top' by one and then set the element at the 'top' index of the array to be the element you want to add.

When you want to remove (pop) an element from the stack, you first check if the stack is empty (i.e., if 'top' is equal to -1). If it is not empty, you simply decrement 'top' by one.

To get the top element of the stack (peek), you simply return the element at the 'top' index of the array.

To check if the stack is empty, you check if 'top' is equal to -1. If it is, the stack is empty. If it is not, the stack is not empty.

This is a simple and efficient way to implement a stack data structure using an array.