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‫So in this video, we're going to do the introduction to delete last.

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‫And in the next video, we'll write the code for this function.

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‫And the reason I split this into two videos is because removing and deleting the last item in a linked

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‫list is far more complicated than adding an item to the end of the linked list.

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‫So to explain, I'm going to bring up a link to list like this.

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‫And we have three situations to code for.

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‫First, if we have two or more items, we're going to move tail over to the previous node and delete

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‫the node at the end of the length list.

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‫We also have to code for when we have an empty linked list, but we also have another edge case for

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‫when we have one item in the length list.

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‫So if you want to challenge, pause the video here and see if you can code this function.

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‫Otherwise, I'm going to get into the steps for removing a node when we have two or more items in the

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‫linked list.

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‫So it looks easy to move tail over to the previous node and then just delete the last node.

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‫But to explain why this is more complicated than it looks, I'm going to put this node back, move tail

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‫over and turn this length list into a set of unordered maps.

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‫So this is very similar to the way Linked list would work.

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‫So what we're wanting to do is move tail up to this node and then we'll set tail next to be equal to

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‫null pointer and delete that last node.

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‫But let's put everything back and look at what we need to do to make that happen.

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‫In order to set tail to be equal to this node, we need to set tail equal to a pointer that points at

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‫this node.

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‫And the only pointer that points at it is next in this node.

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‫So that means we need to get to this node.

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‫And the only way to get to this node is through next in this node and so on until we get to the head.

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‫So we have to have a pointer that starts at the head and then iterates through the length list until

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‫it gets to this node.

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‫And then we can set tail to be equal to this pointer.

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‫Then we can set tail next to be equal to null pointer and delete the last node.

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‫So let's put this back to its graphical form.

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‫And in order to do this, we're going to create a couple of variables called pre and temp will set them

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‫equal to head.

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‫And for now I'm going to remove head and tail and I'm going to move pre underneath and we're going to

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‫create a loop that goes until temp.

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‫Next is equal to null pointer, which will end up happening when we get to the end of the length list.

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‫So we start out by saying temp next.

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‫If that's pointing to a node, we're going to set pre equal to temp, and in the first iteration it's

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‫already equal to temp, and then we'll set temp to be equal to temp next.

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‫And that moves that over.

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‫And then we're going to do it again.

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‫We move pre up temp over and then we just keep iterating through the linked list and this will be the

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‫last time we do this.

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‫We move pre up temp over.

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‫Now temp next is equal to null pointer that breaks us out of our loop and pre and temp.

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‫Stay right here.

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‫So for now I'm going to remove temp and we'll set tail to be equal to pre and that's the only thing

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‫we're using pre for.

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‫So I'm going to drop that out.

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‫We'll set tail next to be equal to null pointer that breaks that node off of the end of the length list.

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‫And I want to bring back temp.

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‫Remember it was pointing to this node.

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‫We will say delete temp and that removes that node.

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‫So we will code this in the next video.

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‫But for now that is our introduction to delete last.