The Resistance | Think Like A Coder, Ep 2

View full lesson: https://ed.ted.com/lessons/the-resistance-think-like-a-coder-ep-2

This is episode 2 of our animated series “Think Like A Coder.” This 10-episode narrative follows a girl, Ethic, and her robot companion, Hedge, as they attempt to save the world. The two embark on a quest to collect three artifacts and must solve their way through a series of programming puzzles.

Lesson by Alex Rosenthal, directed by Kozmonot Animation Studio.

After breaking Ethic out of prison,

Hedge flies them both towards
a frontier settlement

in the shadow of the Bradbarrier,
the great wall that encircles the nation.

All the settlers there will soon gather
for the monthly feeding.

The people of the wall spend their days
gathering up works of art and literature,

from all across the land.

On feeding day, the furnace-bots arrive,
ravenous.

If they eat, the lights stay on,
and the food gets delivered.

If they starve, the people do too.

Hedge’s fuel supply runs out just as he
and Ethic reach the outskirts of town,

and they come in for a crash landing.

Luckily, everyone is too busy preparing
for the feeding to notice.

Today’s feeding is where Ethic
can find the leader

of an underground resistance movement.

This person knows the location of the
first of three powerful artifacts.

The problem is, Hedge and
Ethic don’t know

the resistance leader’s name
or appearance.

But Hedge has gathered the
following information:

The leader has green eyes.

If the leader has red hair, their name has
at least one consecutive double letter.

If the leader wear glasses,
their name has exactly 2 vowels.

Otherwise, their name has
exactly 3 vowels.

There is exactly one person for whom
these are all true.

As a fugitive,

Ethic can’t sneak into the crowd without
drawing attention to herself.

But she can give instructions to Hedge.

And one tool she has is what
programmers call a conditional.

That’s a statement of the form
“If A, then B.”

Flowcharts are great illustrations
of how those work.

This conditional translates to:
if A is true, carry out instruction B.

There are also conditionals that account
for different possibilities.

This says, “If A is true, perform
instruction B.

Otherwise, carry out instruction C.”

So what instructions does she give Hedge
so he can find the resistance leader?

Pause now to figure it out for yourself.

With a problem like this,
it can help to simplify first.

What if Hedge just has to examine
this one person?

What information does he need
to collect about her?

He might ask, “Does she have green eyes?”

What other questions should Hedge
ask to find the resistance leader,

and how can he track those answers?

Pause now to figure it out for yourself.

It may seem intuitive how you’d approach
this problem as a human.

But Hedge isn’t a human,

and so the challenge comes from needing
to give him systematic instructions

that will work in any scenario.

Hedge needs to examine the settlers,
one at a time,

until he discovers the right person.

In other words, like with the
lock on the prison cell,

this is a loop that repeats the
same instructions.

Only this time the loop will involve
a series of questions

in the form of conditionals,

and will end as soon as Hedge
finds his target.

But first, you’ll want to organize
your information.

Each person has a set of characteristics:
Eye color, hair color, glasses, and name.

Does this person have green eyes?

If so, mark a check next to “eye color."
If not, mark an X there.

If they have red hair, does their
name contain a double letter?

If so, mark a check next to “hair color.”

If they don’t have a double letter,
mark an X next to “hair color.”

Anyone with red hair and no double
letter can’t be the resistance leader.

But notice that if they have blue hair,

Hedge will skip this question and
go on to the next one.

For the last question, we can say,

“If they wear glasses, does their name
have exactly 2 vowels?

If they don’t have glasses, does their
name have exactly 3 vowels?”

There will be people in the crowd with
glasses and 1 vowel,

or no glasses and 2 vowels.

But they’re not who we’re looking for,
so they’ll get X’s.

The resistance leader must be someone
with either check marks

or blanks next to every question.

Blanks are ok, because if someone
has blue hair,

the rule about red hair doesn’t
apply to them.

You could have Hedge ask every question
about every person,

and then choose the person with
only checks and blanks.

But there’s a way to save yourself lots
of time: as soon as Hedge marks an X,

have him move on to the next person.

You don’t need to know the answer
to every question;

just one X means they’re not the target
of your search.

Hedge buzzes through the crowd,

and within minutes finds Adila,
the resistance leader,

and brings her back to Ethic.

Adila agrees to help them steal the first
artifact— the node of power—

but under one condition:

that Ethic and Hedge jump-start
the revolution

by reprogramming the furnace-bots
that terrorize the town.

And right on cue, the robots descend.