text stringlengths 1 81 | start float64 0 10.1k | duration float64 0 24.9 |
|---|---|---|
Many years ago when Shawn, who
has since graduated, came up. | 1,017.15 | 3.84 |
Was asked the same question. | 1,020.99 | 1.2 |
So Derek, you are in this
wonderful history of students | 1,022.19 | 2.614 |
who have tried this demonstration. | 1,024.804 | 1.416 |
This was, as you can, see before
we had touchscreen technology. | 1,026.22 | 2.49 |
So we had sheets of
paper up on the screen. | 1,028.71 | 1.791 |
But the idea was the same. | 1,030.501 | 1.389 |
And Shawn is perhaps one of
our favorite memories in so far | 1,031.89 | 3.24 |
as he, too, was asked to solve
the same problem in his way. | 1,035.13 | 3.014 |
[AUDIO PLAYBACK] | 1,038.144 | 0.666 |
-OK, so your task here,
Shawn, is the following. | 1,038.81 | 3.33 |
I have hidden behind
these doors the number 7. | 1,042.14 | 4.199 |
But tucked away in some of these doors
as well are other non-negative numbers. | 1,046.339 | 4.221 |
And your goal is to think
of this top row of numbers | 1,050.56 | 2.45 |
as just an array, or just a
sequence of pieces of paper | 1,053.01 | 2.87 |
with numbers behind them. | 1,055.88 | 1.14 |
And your goal is only using the top
array here, find me the number 7. | 1,057.02 | 4.09 |
And we are then going to critique
how you go about doing it. | 1,061.11 | 3.43 |
Find us the number 7, please. | 1,064.54 | 1.671 |
No. | 1,075.975 | 0.5 |
5, 19, 13. | 1,080.04 | 4.043 |
It's not a trick question. | 1,090.24 | 1.105 |
1. | 1,094.775 | 0.5 |
At this point, your score is not very
good, so you might as well keep going. | 1,100.168 | 3.166 |
3. | 1,106.17 | 0.5 |
Go on. | 1,111.84 | 0.69 |
-[INAUDIBLE]. | 1,112.53 | 0.677 |
-Frankly, I can't help but wonder
what you're even thinking about. | 1,113.207 | 2.75 |
Only the top row. | 1,118.7 | 0.85 |
So you got 3 left. | 1,119.55 | 0.95 |
So find me 7. | 1,120.5 | 2.475 |
-[INAUDIBLE]. | 1,122.975 | 0.541 |
-17. | 1,140.33 | 2.049 |
-[INAUDIBLE]. | 1,142.379 | 0.541 |
-7. | 1,150.711 | 0.499 |
[END PLAYBACK] | 1,151.21 | 1.695 |
SPEAKER 1: All right. | 1,152.905 | 0.875 |
So we don't ask people
to search for 7 anymore. | 1,153.78 | 2.65 |
But this invites the
question, how are we | 1,156.43 | 2.74 |
allowed to have that assumption, right? | 1,159.17 | 2.12 |
I've been assuming in week 0 that
the phone book was alphabetized. | 1,161.29 | 3.35 |
And therefore, I can find Mike Smith
really fast in logarithmic time. | 1,164.64 | 3.37 |
And we were just assuming
a moment ago that we | 1,168.01 | 2.12 |
could find the number 50 super-fast
because of divide and conquer. | 1,170.13 | 3.62 |
Again, but only if
that array were sorted. | 1,173.75 | 2.71 |
Indeed, Derek technically
just got lucky in so far | 1,176.46 | 2.22 |
as he found 50 the
first time in 3 steps. | 1,178.68 | 3.012 |
But it could have been as many as
7 steps because it was, indeed, | 1,181.692 | 2.708 |
a random algorithm. | 1,184.4 | 0.96 |
Or even if he had used linear search. | 1,185.36 | 2 |
So suppose we want to
actually sort something. | 1,187.36 | 3.34 |
So these are still used
on campus sometimes. | 1,190.7 | 2.27 |
So these are blue books for exam period. | 1,192.97 | 2.112 |
And suppose that we're at the end of
a semester and a bunch of students | 1,195.082 | 2.958 |
have written their
names on these things. | 1,198.04 | 1.708 |
And so A's and B's and C's and D's. | 1,199.748 | 2.202 |
And suppose that they're handed
in at somewhat random times. | 1,201.95 | 2.64 |
There's always that kid who hands
in his or her exam at an hour | 1,204.59 | 2.43 |
into the 3-hour exam,
and then most of them | 1,207.02 | 1.57 |
come in around like 2 hours 45 minutes. | 1,208.59 | 1.84 |
And so therefore, they're all
in this pretty random arbitrary | 1,210.43 | 4.04 |
order like this. | 1,214.47 | 1.307 |
Actually, if I just them down like
that, they're not really random at all. | 1,215.777 | 3.083 |
And so they're just
in some random order. | 1,218.86 | 2.04 |
And the goal at hand, ultimately,
is for the head TF, for instance, | 1,220.9 | 2.81 |
or the professor to actually
sort all of these blue books | 1,223.71 | 2.719 |
and come up with an alphabetical order
so you can make sure that everyone | 1,226.429 | 3.041 |
has actually submitted on time. | 1,229.47 | 2.06 |
So how do we do this? | 1,231.53 | 1.54 |
What is the algorithm
with which to do this? | 1,233.07 | 2.84 |
Because indeed, if he
or she, the professor, | 1,235.91 | 2.17 |
later wants to find a certain
name of the alphabet, like Smith, | 1,238.08 | 4.15 |
it'd be nice if they don't have to sift
through all 26, or all 100, or all 500 | 1,242.23 | 4.03 |
blue books. | 1,246.26 | 0.5 |
They can just jump
roughly to the middle, | 1,246.76 | 1.71 |
and then divide and conquer
and find Smith there after. | 1,248.47 | 2.41 |
Can we get one volunteer to
come up and propose how to sort? | 1,250.88 | 3.46 |
You want come on up? | 1,254.34 | 0.97 |
Come on up. | 1,255.31 | 0.64 |
What's your name? | 1,255.95 | 0.43 |
AUDIENCE: Allison. | 1,256.38 | 0.8 |
SPEAKER 1: Allison. | 1,257.18 | 1.08 |
All right, come on up. | 1,258.26 | 2.15 |
So if you've ever
sorted something before, | 1,260.41 | 1.75 |
now's your chance to
show that off, Allison. | 1,262.16 | 1.941 |
All right. | 1,264.101 | 0.499 |
So here are a whole bunch of blue books. | 1,264.6 | 1.66 |
And I've just arbitrarily written
not names, but first letters | 1,266.26 | 2.14 |
of the alphabet on them. | 1,268.4 | 0.999 |
So go ahead and sort them. | 1,269.399 | 1.381 |
AUDIENCE: So I start with a letter. | 1,270.78 | 2.415 |
And if this is before
that, I just put it on top. | 1,273.195 | 2.502 |
SPEAKER 1: OK. | 1,275.697 | 0.583 |
So that's X and L. Gotcha. | 1,276.28 | 1.614 |
AUDIENCE: And because Z is after that-- | 1,277.894 | 0.828 |
SPEAKER 1: There's Z. | 1,278.722 | 0.828 |
AUDIENCE: --I put it below. | 1,279.55 | 1.124 |
And D is here. | 1,280.674 | 1.181 |
SPEAKER 1: OK. | 1,281.855 | 0.584 |
So you seem to be taking them one at a
time and just dealing with the problem | 1,282.439 | 3.207 |
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