What is a Stack?

A stack is a data structure that consists of Nodes. Each Node references the next node in the stack, but does not reference it’s previous.

Common terminology for a stack is

• Push - Nodes or items that are put into the stack are pushed

• Pop - Nodes or items that are removed from the stack are popped

• Top - This is the top of the stack.

• isEmpty - checks if the stack is empty or not.

• Peek - When you Peek you will view the Top node in the stack. If the stack is empty, and you don’t Peek, you will receive a NullReferenceException if you attempt to Pop. Stacks follow these concepts:

• FILO concept: First In Last Out. This means that the first item in the stack, will be the last item out.

• LIFO concept: Last In First Out This means that the last item in the stack, will be the first item out.

What is a Queue?

Common terminology for a queue is

• Enqueue - Nodes or items that are added to the queue.
• Dequeue - Nodes or items that are removed from the queue.
• 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 Top node in the stack. If the stack is empty, and you don’t Peek, you will receive a NullReferenceException.

Queues follow these concepts:

• FIFO - First In First Out - This means that the first item in the queue will be the first item out of the queue.
• LILO - Last In Last Out - This means that the last item in the queue will be the last item out of the queue.