1
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‫So now we're going to write, insert and insert starts out like this.

2
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‫We're going to insert a new node with a particular value at a particular index.

3
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‫So let's bring up a doubly linked list like this.

4
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‫We'll create a new node.

5
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‫And just as we've seen before, we can't have anything out of range for the indexes, so we can't have

6
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‫anything less than zero or greater than the length.

7
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‫So we'll say if index is less than zero or index is greater than the length will return false.

8
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‫And if we're inserting the node at the index of zero, we'll use pre to do that.

9
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‫And if we're going to insert it at the index of four or in this case the length will use the append

10
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‫function to do that.

11
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‫So now let's look at all of these if statements.

12
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‫So now let's bring back our doubly linked list and look at how we insert this node in the middle of

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‫this linked list.

14
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‫So I'm going to put this back.

15
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‫And in order to do this, we'll need a couple of variables.

16
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‫One of them, I'll call after that will go after where we're inserting this.

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‫And the other one I'll call before and we'll put this new node in between both of those.

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‫So we have three new items here that we need to create.

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‫First, we need to create this node and the before variable will set that equal to get at index minus

20
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‫one.

21
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‫And we could use the get function for after.

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‫But that is not best practice because get is o of NW and you can point after at the appropriate node

23
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‫by setting it equal to before next.

24
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‫And doing it this way is o of one.

25
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‫So now let's look at these three lines of code and with the rest of our code.

26
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‫And now let's bring back our doubly linked list.

27
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‫I I'm going to just move these apart like this.

28
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‫And we're going to write four lines of code that are going to redirect these four arrows.

29
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‫And when we do that, it'll end up looking like this.

30
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‫So for now, let's put this back and we'll start by redirecting the arrows previous and next on the

31
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‫new node.

32
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‫So we'll start out like this new node, previous equals before.

33
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‫So we're going to take that previous arrow on the new node and point it at the same node that before

34
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‫is pointing to.

35
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‫Then we'll say new node next equals after.

36
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‫Now we're going to take the next pointer from the new node and point it at the same node that after

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‫is pointing to.

38
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‫There will say before next equals new node that is before next equals new node.

39
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‫And we'll say after previous equals new node that is after.

40
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‫Previous.

41
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‫Equals new node.

42
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‫And that adds this node and to our doubly linked list.

43
00:03:15,520 --> 00:03:21,550
‫So these four lines of code have redirected these four arrows.

44
00:03:21,940 --> 00:03:25,160
‫So now let's look at this and with the rest of our code.

45
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‫And now we just need to increase the length by one, and then we'll return.

46
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‫True.

47
00:03:32,140 --> 00:03:35,440
‫So that is the entire insert function.

48
00:03:35,440 --> 00:03:38,410
‫We'll look at this code in a moment in V's code.

49
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‫And when we do, we're going to create a linked list with nodes with a value of one and three, and

50
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‫then we'll run insert at the index of one with a value of two.

51
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‫And then our linked list will be one, two, three.

52
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‫So now let's flip over and take a look at this.

53
00:03:58,540 --> 00:04:07,150
‫So there is our insert member function added to our doubly linked list class and I'll scroll up and

54
00:04:07,150 --> 00:04:13,810
‫in our main function that creates that linked list with a values of one and three, and then with this

55
00:04:13,810 --> 00:04:16,900
‫line will print that out and I'll run this.

56
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‫And you can see that we have values of one and three.

57
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‫So then I'm going to come up here and add a line.

58
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‫And this will insert at the index of one a node with a value of two.

59
00:04:31,070 --> 00:04:34,700
‫And then we'll print this out and I'll run this again.

60
00:04:35,340 --> 00:04:40,650
‫And now our doubly linked list has values of one, two and three.

61
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‫And that is our function for insert.