Earth | Ana

[anakp07]

Stacks and Queues

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Comprehension Questions

Question	Answer
What is an ADT?	An Abstract Data Type is an object which is described by the methods it has and how they perform. It has a public interface but implementation details are private.
Describe a Stack	A Stack is a data structure which stores a list of data and only provides access in a Last-In-First-Out (LIFO) order.
What are the 5 methods in Stack and what does each do?	The initialize method which starts the stack. push(item) - This method puts an item into the stack at the top. pop - This method removes and returns the item on the top of the stack. is_empty - This method returns true if the stack is empty and false otherwise. To_s - Turns implementation into readable format
Describe a Queue	A queue is like a stack but it operates in a first-in-first out order. Like a line of people at a concert, the first element to enter the queue is the first element removed.
What are the 5 methods in Queue and what does each do?	Initialize which creates array of specified size. enqueue(item) - This method puts an item into the back of the queue. dequeue - This method removes and returns the item at the front of the queue. is_empty - This method returns true if the queue is empty and false otherwise.
What is the difference between implementing something and using something?	Implementing is the details in how you choose to make something work. Using something is how you expect the the method to perform.

OPTIONAL JobSimulation

Question	Answer
Did you include a sample run of your code as a comment?

[CheezItMan]

Ana, you hit the main learning goals here. I had a few comments and let me know if you have questions on them.

[CheezItMan]

Why the -1 in @front - 1 and @size - 1?

[CheezItMan]

👍

[CheezItMan]

👍

[CheezItMan]

⚠️ This gives ths size of the store and not the size of the stuff in the queue.

[CheezItMan]

Suggested change

	return @front == -1 || @front == @back
	return @front == -1

If you add 1 element with your algorithm, front will equal back (and you still have 1 thing in the queue).

[CheezItMan]

Could you handle this using:

i = (i + 1) % @SiZe

in a simpler manner.

[CheezItMan]

👍