6: Stack

Stack
Introduction
Stack is a list of items in which all insertions and deletions are made at one end, called the top. Stack is a data
structure that is particularly useful in applications involving reversing.

LIFO : Last In First Out
Stack Implementation
Stack can be implemented in two different ways:
1. Contiguous stack: the stack is implemented as an array.
2. Linked stack: pointers and dynamic memory allocation is used to implement the stack.
Stack Operations
Initialise: creates/initialises the stack
push(e): Insert element e, to be the top of the stack.
pop(): Remove from the stack and return the top element on the stack; an error occurs if the stack is empty.
size(): Return the number of elements in the stack.
isEmpty(): Return a Boolean indicating if the stack is empty.
top(): Return the top element in the stack, without removing it; an error occurs if the stack is empty.