Stacks and Queues

Stacks

A stack is a data structure that consists of Nodes. Each Node references the next Node in the stack

Common terminology for a stack :

you would check isEmpty before pop – Top – peak functions

FILO (First In Last Out) : that mean that first item added in the stack will be the last item popped out of the stack

Steps to add new item to Stack :

Select new free node
assign the next property of new Node to reference the Node that old top of Stack .
re-assign reference Stack top to the new node

Steps to remove top item from Stack :

create a reference named temp that points to the same Node that top points to
re-assign top to the value that the next property of old top
remove old top Node safely by clear out the next property in your current temp reference
return the value of the temp Node that was just popped off.

When you pop something from the stack , the item that will removed is last one appended

## Queues

Enqueue - Nodes or items that are added to the queue.
Dequeue - Nodes or items that are removed from the queue. If called when the queue is empty an exception will be raised.
Front - This is the front/first Node of the queue.
Rear - This is the rear/last Node of the queue.
Peek - When you peek you will view the value of the front Node in the queue. If called when the queue is empty an exception will be raised.
IsEmpty - returns true when queue is empty otherwise returns false.

The principle of FIFO (First In First Out) is applied to Queue

process of adding a Node to a queue: