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‫So now we're going to write our code for our pivot helper function.

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‫We're going to run it on this array, which I will shrink down into the corner.

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‫And the first thing I want to talk about with Pivot is that there are two different places where we

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‫swap items in the array, and we can do that with something like this.

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‫But because we do it twice in the pivot function, I don't want to write this code twice, so I'm going

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‫to break this out into its own function that I call swap and then we'll pass it the array and the two

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‫indexes that we want swapped.

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‫And like I said, we will use this in two different places in the pivot function.

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‫So now let's start writing Pivot.

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‫We will pass this the array, and then we will pass it a pivot index and an end index.

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‫And for what we're going to do in this video, the pivot index will be the index of zero and the end

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‫index will be the index of six, which is the last item in the array.

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‫So this pivot index I'll represent with this arrow and I just put pivot on the arrow, but I like to

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‫call the variable name Pivot Index to emphasize that this is an index, not the value of the item at

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‫that index.

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‫And then we'll say swap index equals pivot index like this.

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‫And on the arrow, I'll just write swap.

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‫But this is the variable swap index.

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‫And then we have a for loop that goes from pivot index plus one to the end index.

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‫So I is going to be here.

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‫And then in the for loop we'll say if array at the index of I is less than array at pivot index.

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‫And in this first iteration of the for loop, the conditional in this if statement is going to be false

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‫because six is greater than four.

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‫So I'll color that in gray.

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‫We'll run the for loop again, which moves I up to here.

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‫Now the conditional in the if statement is true.

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‫So inside of this, if statement will move swap index up one like that and then we'll run that swap

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‫function that we created at the beginning of the video.

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‫Like this we pass it the array and swap index and I and it swaps those two items.

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‫So if you keep running this code the way we have it here, you'll end up with an array that looks like

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‫this.

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‫Then we need to run that swap function one more time.

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‫We'll pass it the array and pivot index and swap index.

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‫And that does this.

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‫Now, the only thing left to do is to return the swap index.

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‫And I want to emphasize in this case, that will be the index of three.

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‫It's not the value of four.

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‫That is at that index.

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‫We are returning the index.

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‫So that is all of our code for pivot.

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‫We'll look at this code in a moment in VTS code.

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‫And when we do, we'll start with an array that looks like this and then we'll run, pivot on it and

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‫we will return that swap index and then look at what the array looks like after we have run.

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‫Pivot on that array.

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‫So now let's flip over to VS code and take a look at this.

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‫So here is our swap function here and I'll scroll up and this is our pivot function here and I'll scroll

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‫up again.

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‫And with this line we create that array with those seven items in it.

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‫And with this line, we get the size of the array.

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‫And down here we run, pivot on that array and we pass it the pivot index and the end index.

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‫And remember, that pivot is going to return an index and we'll store that in this integer called returned

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‫index.

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‫And with this line will print out that return index.

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‫And with this for loop, we will print out the array.

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‫And I'll run this.

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‫And you can see up here that our returned index is three.

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‫And with the array that's been returned, that four is now in the middle.

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‫All of the items that are less than are on the left.

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‫All of the items that are greater than are on the right.

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‫So it looks like we have a working function for pivot.