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‫In this lesson, we will talk about stacks and Qs.

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‫Stacks and Qs are data structures in computer science.

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‫A data structure is a data organization, management and storage format that enables efficient access

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‫and modification.

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‫Each data structure has a unique way of storing and managing the data we insert into it.

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‫There are many different types of data structures, but in this lesson we will look at two that are

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‫very common and come in handy when we want to deal with data in some scenarios.

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‫The first data structure we will talk about is the stack from its name.

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‫A stack stores the data in the form of a stack.

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‫If we look at this picture of the rock stacked on top of each other, we can easily take the first rock

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‫without causing a stack of rocks to fall.

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‫But it's impossible to take out the ones in the middle.

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‫We can easily take the first rock without causing the stack of rocks to fall, but it's impossible to

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‫take out the ones in the middle.

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‫So it's first come last out or last in.

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‫First out a stack basically adds and removes data from the top only.

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‫So this concept stacks are usually or very often used in mathematical algorithms and in data management

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‫by the operating systems.

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‫So some examples on using stacks that we might face are, for example, reversing data.

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‫So for reversing data or numbers using a stack, it is very simple.

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‫If we just take the input from the user, for example, and store it in a stack, then start removing

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‫data from the stack from top so that the data will get reversed.

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‫So then there are browser back buttons, for example.

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‫So while watching tutorials and tutorials you, your browser will save the website slash web pages you

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‫clicked on and pressing the back button will load the last page you went to.

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‫And then the one before it, which hereby is a textbook example of one, is that can come in handy.

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‫And then there are also the undo and redo buttons that you have in many applications where you have

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‫a stack basically storing what was performed and then undoing that performed action.

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‫So both stacks and Q's are collections like lists and dictionaries.

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‫Stacks have their own unique operations that we can use, for example, to manipulate and manage the

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‫data.

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‫And they store the ones that we're going to look at are going to be pushed.

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‫So using the push method, we can add data to the stack.

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‫Of course, the data will always be added on top.

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‫Then we have pop and using the pop method we can remove data from the top of the stack.

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‫And finally we have the peek method which will return the object data on top of the stack without removing

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‫it.

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‫So then there are queues and choose are another type of data structures that is commonly used in programming

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‫QS work like real Qs in real life, like an airport check in where the first person in the front desk

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‫gets served first, or like in a restaurant drive thru where the car in the front will get to order

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‫first and when new cars come in they must wait in the back of the line and we'll be last served.

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‫So we use Qs when the order the data comes in is important.

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‫So data can be added only from the back and removed from the front and can't access the elements in

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‫the middle.

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‫It's the FIFO system.

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‫So first in, first out, for example in operating systems, queuing messages, IO requests, mouse

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‫movements and so forth so they can be executed in the order they came in.

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‫Then managing web requests and a server to handle them one by one.

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‫So it's a handle congestion and queuing input in video games, for example, and a fighting game with

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‫combo attacks like Street Fighter, where you have to keep track of the user input to determine the

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‫combo that will be performed.

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‫Jews have their own unique operations that we can do on them to manipulate or manage the data they store.

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‫For example, using the NQ method, we can add data to the queue.

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‫Of course the data will be always added to the back of the queue, so it will be rare.

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‫So at the rear, so to speak.

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‫Then we have the queue method.

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‫We can remove data from the front of the queue using the queue method.

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‫And finally we have the peak method which will return the object or data in the front of the queue without

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‫removing it.

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‫So you're just peeking in, but you're not doing anything else with it, just looking what is there?

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‫And then you can use it.

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‫So next we are going to look at how we can actually implement and use stacks and queues in C-sharp.