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So, [COUGH] let's do a couple more little
exercises

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that get you sort of in the mind set

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of being a programmer, and how programmers
tend to

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have to think about problems a little bit
differently.

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So, here we go.

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This I call this An Animated Short Story.

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And your job, I'm going to just give you a
differ, several sets of numbers.

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And I want you to find the largest number
in a list of numbers.

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Now, it's not so important to know what
the large

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number is, but also to think about how
your mind

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attacks the problem.

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What your eyes are doing.

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What your mind is doing.

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How you break a bigger problem down into
smaller problems.

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How a human solves this problem.

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And then we'll focus on how a computer

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might have to look at the problem
differently, okay?

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So don't just, like, get the answer.

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That's not so important.

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Think about how you get the answer.

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So, don't just like scroll ahead in your
YouTube and cheat and go get the answer.

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Think about actually solving the problem,
and then

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monitor what your brain is thinking as it
goes.

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So, here we go.

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So, I'm going to give you a list of
numbers,

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and you are to tell me what the largest
number is.

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Ready?

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Set, go.

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[BLANK_AUDIO]

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[SOUND] I didn't make it easy, you're
looking for the largest number.

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[BLANK_AUDIO]

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Did you get it?

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Did you have to go back a couple of times?

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Actually I don't care what the answer is.

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The question is

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How was your brain solving?

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Okay, you probably want to know what it
is.

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The answer is 198, that was the largest
number.

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Of course what I was doing is I was moving
it to make it difficult.

40
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But here's the thing, how do humans look
at this?

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Like, do humans, like, did you look at 25,
then you looked at 1, then you looked

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at 114, and then did you just look at them
slowly one at a time, like this?

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Or no, I doubt it.

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If you are, maybe you're a computer.

45
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Maybe I'm talking to computers, maybe
you're all computers.

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I'm certainly not a computer, maybe you're
all computers.

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Okay, enough of that.

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No, that's probably not how you did it.

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What you probably did was you had your

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eyes move around the whole thing very
rapidly.

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And the first thing that you figured out
is that there

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were one-digit blobs, there were small,
medium, and large blobs of purple.

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And the first thing you knew, right away,
was there

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was no point at looking at any of the
small blobs.

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Your brain just threw the blobs away
really quick.

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Then you say, okay, given that it,

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there's no four-digit numbers, they're
three-digit numbers.

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Then what you probably did is you started
looking for the first digit.

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You say, look, there's some ones.

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Is there any twos?

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Quickly, you decided there are no twos.

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So you knew that you had to look for the
big blobs.

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And the second digit was probably the
thing that mattered.

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Then you start getting to the nine, you
say, okay, there's some nines.

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So that means it's, it's one, nine,
something.

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Then that was the part that you probably
had to go

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check to find the, oh, where the heck was
the 190, aah!

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Oh, 198 right there, [LAUGH] yeah I color

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coded it, and I couldn't even see it,
okay?

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But the point is, is, humans are great

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at eliminating sort of bad solutions,
really fast.

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And you probably looked at how big, how
much purple was on

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the screen, eliminating the areas that
were less purple, because you knew that

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your brain quickly and instinctively
knew that

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the more purple meant a larger number.

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Computers don't do any of that, they don't
do any of that.

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So, in order to make you feel a little
more like a computer, I have another test.

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And again, the goal is not just to find
the largest number.

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But to monitor as you go, what your brain
is thinking, while you're doing this, okay?

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Do you get it?

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How are you attacking the problem, what is

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your feeling as you're attacking the
problem?

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Are you a computer or not?

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Here we go.

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I'm only going to give you a few seconds.

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[BLANK_AUDIO]

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[SOUND]

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So, what did

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you get?

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00:05:05,230 --> 00:05:10,090
My guess is that most of you just said, I
don't care.

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This is such a hard problem.

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It's a stupid problem.

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Or I'll try and turn my head upside down,
or something.

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It's a really hard problem.

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The other one was kind of easy.

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Not that you, you might not have got it,
but you

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had this natural instinct that allowed you
to approach the problem.

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Okay, I'll show you what the right answer
is.

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The right answer is.

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Right there is 197.

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Yay.

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Right.

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I, you can't even, even if I tell you to

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you know there you are you know, what is
this?

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Is this 500 or two zero zero.

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Actually, the only way I can do this is I
flip it to find it.

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I mean it's just not what humans are good
at.

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This is a little bit more like how
computers see the world.

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But the fact that the data's frontwards or

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backwards should sort of make no
difference, right?

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Computers need a strategy, we need to give
them a strategy.

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Okay.

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So here we go.

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[COUGH]
One last experiment.

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Now I'm going to show you numbers one at a
time.

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And at the end, I want you to tell me what
the largest number that you saw was.

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Ready?

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Here we go.

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First number.

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What was the largest number?

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As a matter of fact,

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how did you solve that
problem?

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You solved that problem most likely
because you didn't, you couldn't look

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at all the numbers at the same time, so
you probably created

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a variable in your head without even
knowing.

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And you put into that variable.

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You call the variable, the largest number
I've seen so far.

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And you haven't seen any, so let's say the

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largest number you've seen so far is
negative 1.

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Then I show you 3 and you said to
yourself.

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Well.

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Negative 1 is no longer the largest number
I've seen.

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So I'm going to keep that one,
I'll keep 3.

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That's the largest I've seen so far.

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And now I see 41, 41 is larger than 3
so I will keep that.

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And now I see 12, now 12 is crap because
it's nowhere near as good as 41.

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So I'm keeping 41.

138
00:07:52,600 --> 00:07:53,475
74. Oh, 9.

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9, not nearly as good as 41, so I'm
gonna throw that one away.

140
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74, better, better.

141
00:08:01,570 --> 00:08:02,190
Keep it.

142
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Keep that one.

143
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So I'll keep 74.

144
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And the last number is 15.

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Don't even know it's the last number, but,
we don't want to keep that one.

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And so now, we're done.

147
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So we know that at the end, what was
during the loop the largest so far is

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the actual largest of all the numbers, and

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we don't remember exactly how many numbers
there were.

150
00:08:23,980 --> 00:08:26,380
So that's kind of like thinking like a

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program, you know, this kind of sliding
window.

152
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Didn't matter if I gave you a billion
numbers or five numbers.

153
00:08:32,580 --> 00:08:34,920
I think there were five numbers, actually.

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This notion of the largest so far is a
powerful notion.

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As a matter of fact, it's central to the
program I've been showing you.

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And I don't want you to try to understand
this, but this part in the purple.

157
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This part in the purple is really saying,

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I'm going to loop through the counts of
all the words.

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So it's got a word like "the" is 15
times, and "clown" is four times.

160
00:09:02,310 --> 00:09:06,590
And it's going to look through all the
pairs of word-value combinations.

161
00:09:06,590 --> 00:09:08,000
And it's going to basically say, I'm

162
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going to go through the counts that I
have.

163
00:09:10,860 --> 00:09:12,590
And I'm going to check to see if the count
I'm looking at

164
00:09:12,590 --> 00:09:16,730
is bigger than the biggest count I've
seen so far.

165
00:09:16,730 --> 00:09:19,330
And if it is, I'm going to remember it.

166
00:09:19,330 --> 00:09:20,490
Now, don't worry about this.

167
00:09:20,490 --> 00:09:21,960
We haven't even covered any of this stuff.

168
00:09:21,960 --> 00:09:24,700
That's what chapter two, three, four,
five, six.

169
00:09:24,700 --> 00:09:30,250
But this is an algorithm, a paragraph, a
pattern.

170
00:09:30,250 --> 00:09:33,430
That allows you to find the largest
number, and we'll

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00:09:33,430 --> 00:09:37,270
look at this again in great detail in
upcoming chapters.

172
00:09:37,270 --> 00:09:39,680
So this is kind of thinking like

173
00:09:39,680 --> 00:09:42,960
a computer, having a sliding window across
the

174
00:09:42,960 --> 00:09:45,970
long list of numbers, and coming up with

175
00:09:45,970 --> 00:09:49,370
something that is the answer that you
need.

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Okay, so that's the end of this lecture.

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00:09:55,570 --> 00:09:59,080
Read Chapter One, write your Hello World
program.

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Make sure if you haven't, get Python
installed.

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00:10:02,560 --> 00:10:05,470
As you read this chapter and even as you

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00:10:05,470 --> 00:10:08,930
install Python, and even as you write the
first program,

181
00:10:08,930 --> 00:10:11,240
don't get too stuck on the details.

182
00:10:12,340 --> 00:10:15,410
I was confused for like eight weeks or six

183
00:10:15,410 --> 00:10:19,490
weeks in my first programming class;
you'll be confused too.

184
00:10:19,490 --> 00:10:21,870
Just sort of wander through with me, keep
at it.

185
00:10:22,880 --> 00:10:25,690
It will start making sense at some point
that's up

186
00:10:25,690 --> 00:10:28,900
to you, I can't tell you when it's
going to make sense.

187
00:10:28,900 --> 00:10:32,430
So, if, don't sort of stare at everything
until you get it.

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00:10:32,430 --> 00:10:37,090
Just kind of keep digging in, and keep
understanding, and keep playing and

189
00:10:37,090 --> 00:10:41,240
sooner or later this'll make a lot of
sense to you, I promise you.

190
00:10:41,240 --> 00:10:42,010
See you next lecture.