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Now that we know what a stack is, we can start talking about a queue.

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And a queue is very, very similar to a stack because it's also dependent upon a specific order.

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So remember, a stack was LIFO last in first out, a queue instead of being LIFO.

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A queue is going to be FIFO.

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And you might can guess what this is, but this is first in first.

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LB So if we visualize this and we put our cue here and we push ten, we have ten.

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Push 20.

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We have 20.

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Push 30.

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We have 30.

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Push 40.

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We have 40.

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And now if we call Pop, ten is gone.

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If we call pop again, 20 is gone.

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If we push, 50, 50 is there.

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And if we pop one more time now, 30 is gone.

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So that is first in, first out.

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Basically, the oldest item in the queue is taken out.

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So when would something like this be useful?

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Well, I just kind of said it when we want.

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The oldest item.

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Item taken care of.

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So think of this like a line.

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You're standing in line at a store trying to pay.

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Well, the longer you stand in line, you would like to hope that your position in line is getting closer

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and closer to actually being able to pay for your item and check out.

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And that is what a queue is.

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Once you're in that line, you will eventually be the first one that was in the line.

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So you will become the first one out of the line.

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So when we want to get the oldest item taken care of.

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And now that we know what a queue is and that we also know that it's going to be very similar to a stack.

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But instead of being like, Oh, we're going to be FIFO, we're going to go implement our own queue

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so that we can visualize.

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How a QR code differs from a Stax.

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So in the next lecture, we will begin implementing our own Q.