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‫So now we're going to create our append function.

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‫So append with a singly linked list looked like this.

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‫We created a new node.

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‫We had the last node in the linked list point to that new node tail points to that new node and that

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‫adds that into the length list with a doubly linked list that is very similar, except we have these

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‫extra pointers.

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‫So that green pointer there will be the only difference between a singly linked list and a doubly linked

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‫list for the append function.

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‫So we're still going to point that last node to the new node, but we also need to take that previous

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‫pointer from the new node and point it at that last node and then we'll move tail over and that adds

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‫that node into our doubly linked list.

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‫And just like with a singly linked list, we'll also have to code for when we have an empty doubly linked

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‫list.

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‫And when this happens, we'll have head and tail point to that new node.

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‫So we'll start our function off like this.

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‫We pass it a value.

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‫We use that to create a new node.

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‫Like this and we'll code for when we have an empty double length list first where we have head and tail

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‫point to this new node.

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‫So in order to do this, we have to test to see is the length list in fact empty.

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‫And we'll do that by saying if length is equal to zero.

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‫And you could also do this check by saying if head is equal to null pointer and then we'll set head

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‫to be equal to new node like this and we'll set tail to be equal to new node like this.

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‫So let's add this in with the rest of our code we've coded for when we have an empty linked list now

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‫we'll code for when we have items in the length list, we'll say else and let's build out this else

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‫statement and we'll start this out by saying Tail next equals new node that is tail next equals new

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‫node.

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‫And then we'll say new node, previous equals tale.

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‫And that points that previous pointer from that new node at the same node that tail is pointing to.

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‫And then we'll set tail to be equal to new node like this.

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‫And that adds that into our doubly linked list.

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‫So let's add this in with the rest of our code, and the only thing left to do is to increase the length

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‫by one.

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‫So that is our append function.

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

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‫And when we do, we'll start out with a linked list that looks like this and then we'll run, append

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‫and add a second item and our linked list will look like this.

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

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‫So there is our append member function added to our doubly linked list class and then I'll scroll up

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‫and this is our main function.

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‫This creates that doubly linked list with one node with a value of one, and with this line we'll print

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‫that out and I'll run this.

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‫And you can see up here that our linked list has one node with a value of one.

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‫And I'm going to come up here and add a line.

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‫And this will opin that second node with a value of two.

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‫And now I'll run this.

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‫And now we have a doubly linked list with two nodes with a value of one and two.

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‫And that is our function for append.