text stringlengths 1 81 | start float64 0 10.1k | duration float64 0 24.9 |
|---|---|---|
that a fellow educator
made and posted online | 3,358.2 | 2.1 |
that we've abbreviated here to give us
a sense of the difference between stacks | 3,360.3 | 3.99 |
and queues. | 3,364.29 | 0.709 |
[AUDIO PLAYBACK] | 3,364.999 | 0.666 |
[MUSIC PLAYING] | 3,365.665 | 4.655 |
-Once upon a time, there
was a guy named Jack. | 3,370.32 | 2.91 |
When it came to making friends,
Jack did not have the knack. | 3,373.23 | 3.36 |
So, Jack went to talk to the
most popular guy he knew. | 3,376.59 | 2.98 |
He went to Lou and asked what do I do? | 3,379.57 | 2.6 |
Lou saw that his friend
was really distressed. | 3,382.17 | 2.65 |
Well, Lou, began just
look how you're dressed. | 3,384.82 | 2.46 |
Don't you have any clothes
with a different look? | 3,387.28 | 2.73 |
Yes, said, Jack. | 3,390.01 | 0.97 |
I sure do. | 3,390.98 | 1.19 |
Come to my house and
I'll show them to you. | 3,392.17 | 2.46 |
So, they went off to Jack's,
and Jack showed Lou the box | 3,394.63 | 2.96 |
where he kept all his shirts,
and his pants, and his socks Lou | 3,397.59 | 3.22 |
said I see you have all
your clothes in a pile. | 3,400.81 | 2.82 |
Why don't you wear some
others once in a while? | 3,403.63 | 2.53 |
Jack said, well, when I
remove clothes and socks, | 3,406.16 | 3.17 |
I wash them and put them away in
the box, then comes the next morning | 3,409.33 | 4 |
and up I hop. | 3,413.33 | 1.2 |
I go to the box and get
my clothes off the top. | 3,414.53 | 3.18 |
Lou quickly realized
the problem with Jack. | 3,417.71 | 2.73 |
He kept clothes, CDs,
and books in a stack. | 3,420.44 | 2.9 |
When he reached something
to read or to wear | 3,423.34 | 2.45 |
he chose [? the top ?]
book or underwear. | 3,425.79 | 2.62 |
Then when he was done he
would put it right back, | 3,428.41 | 2.41 |
back it would go on top of the stack. | 3,430.82 | 2.49 |
I know the solution,
said a triumphant Lou. | 3,433.31 | 2.49 |
You need to learn to
start using a queue. | 3,435.8 | 2.59 |
Lou took Jack's clothes
and hung them in a closet, | 3,438.39 | 2.81 |
and when he had emptied
the box he just tossed it. | 3,441.2 | 2.84 |
Then he said, now, Jack, at the
end of the day put your clothes | 3,444.04 | 3.25 |
on the left when you put them away. | 3,447.29 | 2.01 |
Then tomorrow morning
when you see the sunshine, | 3,449.3 | 2.51 |
get your clothes from right
from the end of the line. | 3,451.81 | 2.96 |
Don't you see, said Lou. | 3,454.77 | 1.44 |
It will be so nice. | 3,456.21 | 1.49 |
You'll wear everything once
before you wear something twice. | 3,457.7 | 3.4 |
And with everything in queues
in his closet and shelf, | 3,461.1 | 2.85 |
Jack started to feel quite
sure of himself all thanks | 3,463.95 | 3.06 |
to Lou and his wonderful queue. | 3,467.01 | 4.576 |
[END PLAYBACK] | 3,471.586 | 0.982 |
SPEAKER 1: All right, so let's
take a look at another data type, | 3,472.568 | 3.712 |
this one known as a tree. | 3,476.28 | 1.94 |
Because now that we have the ability
to stitch data structures together much | 3,478.22 | 4.16 |
like a linked list, we
now have the ability | 3,482.38 | 1.89 |
to stitch things together not just left
to right or top to bottom conceptually, | 3,484.27 | 5.78 |
but in any number of directions. | 3,490.05 | 1.345 |
And indeed, there's nothing
stopping us from having | 3,491.395 | 2.125 |
one node linked to by way of
multiple pointers, multiple nodes. | 3,493.52 | 4.41 |
So, for instance, this picture here
from a textbook is a tree structure. | 3,497.93 | 4.34 |
And it's very much like the
family trees that you might | 3,502.27 | 2.406 |
have drawn in grade school or the like. | 3,504.676 | 1.624 |
But in this case, you
have just one root node, | 3,506.3 | 2.91 |
the node at the top of the
data structure, so to speak, | 3,509.21 | 2.53 |
from which everything else descends. | 3,511.74 | 2.01 |
And that node is said to have children. | 3,513.75 | 2.26 |
For instance, 2 and 3 are children
of the node number 1 here. | 3,516.01 | 4.06 |
And then there's other semantics in
this world of trees in computer science. | 3,520.07 | 3.52 |
Much like family trees,
anything that does not | 3,523.59 | 2.53 |
have children-- like 5,
6, and 7, or 8 and 9-- | 3,526.12 | 2.7 |
would be called leaves of the
tree, because like the leaves | 3,528.82 | 2.995 |
at the end of the branches,
there is nothing beyond them. | 3,531.815 | 2.375 |
So, nicely enough we borrow
a lot of the language | 3,534.19 | 2.53 |
from family trees and
actual trees in order | 3,536.72 | 2.75 |
to discuss this data
structure known as a tree. | 3,539.47 | 3.14 |
But why in the world would we want
to lay out data in a tree structure? | 3,542.61 | 5.05 |
Now we just seem to be
doing things because we can, | 3,547.66 | 3.06 |
it would seem at first glance. | 3,550.72 | 1.57 |
Because, for instance, suppose we had
these numbers-- 22, 33, 44, 55, 66, 77, | 3,552.29 | 5.14 |
and 88. | 3,557.43 | 1.1 |
They're clearly sorted. | 3,558.53 | 1.1 |
And suppose that I wanted to lay
these out in a data structure | 3,559.63 | 3.27 |
and be able to search them
efficiently, assuming the whole time | 3,562.9 | 4.19 |
that they are indeed sorted. | 3,567.09 | 1.19 |
Well, if we wanted to do that, we have
our old friend arrays from weeks ago. | 3,568.28 | 4.26 |
And we also have our old algorithm
from Mike Smith, our binary search | 3,572.54 | 4.12 |
algorithm, divide and conquer. | 3,576.66 | 1.53 |
And we can find nodes in
this data structure super, | 3,578.19 | 2.52 |
super fast in logarithmic
time, big O of log n. | 3,580.71 | 4.39 |
So, we've solved that problem. | 3,585.1 | 1.67 |
But it turns out we don't necessarily
have to use an array laying out data | 3,586.77 | 5.08 |
from left to right because, again, one
of the prices we pay of using arrays | 3,591.85 | 5.97 |
where as we've realized
today is this finiteness. | 3,597.82 | 3.03 |
At the end of the day, the
size of an array is fixed. | 3,600.85 | 2.56 |
You have to decide in advance how
big your array is going to be. | 3,603.41 | 3.35 |
So, what if you want to
add more numbers to it? | 3,606.76 | 1.999 |
What if you want to remove
numbers for efficiency | 3,608.759 | 2.041 |
and not waste so much memory? | 3,610.8 | 1.46 |
You can't really do that with an array. | 3,612.26 | 1.67 |
You can, but have to
jump through some hoops. | 3,613.93 | 2.54 |
You have to reallocate the array, as
with a function like [? re-alloc ?] | 3,616.47 | 3.47 |
if you indeed used malloc in
the first place to allocate it. | 3,619.94 | 2.93 |
But then you have to copy the
old array into the new array, | 3,622.87 | 2.65 |
so it's all possible. | 3,625.52 | 1.29 |
Nothing's impossible once you
have a keyboard at your disposal, | 3,626.81 | 3.96 |
but it's a lot of work,
and it's more time, | 3,630.77 | 1.96 |
and it's expensive there for
both in terms of your time | 3,632.73 | 2.3 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.