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After breaking Ethic out of prison,

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Hedge flies them both towards 
a frontier settlement

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

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

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

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from all across the land.

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

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

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If they starve, the people do too.

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

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and they come in for a crash landing.

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

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Today’s feeding is where Ethic 
can find the leader

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of an underground resistance movement.

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

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The problem is, Hedge and 
Ethic don’t know

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the resistance leader’s name 
or appearance.

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But Hedge has gathered the 
following information:

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The leader has green eyes.

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

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

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Otherwise, their name has 
exactly 3 vowels.

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

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As a fugitive,

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

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But she can give instructions to Hedge.

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

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

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Flowcharts are great illustrations 
of how those work.

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

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There are also conditionals that account 
for different possibilities.

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

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Otherwise, carry out instruction C.”

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

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Pause now to figure it out for yourself.

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

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What if Hedge just has to examine 
this one person?

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What information does he need 
to collect about her?

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

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

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and how can he track those answers?

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Pause now to figure it out for yourself.

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

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But Hedge isn’t a human,

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

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that will work in any scenario.

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

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until he discovers the right person.

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

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this is a loop that repeats the 
same instructions.

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Only this time the loop will involve 
a series of questions

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in the form of conditionals,

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and will end as soon as Hedge 
finds his target.

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

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

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Does this person have green eyes?

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

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

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

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

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

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But notice that if they have blue hair,

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

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For the last question, we can say,

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

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

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

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or no glasses and 2 vowels.

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

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The resistance leader must be someone 
with either check marks

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or blanks next to every question.

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Blanks are ok, because if someone 
has blue hair,

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

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You could have Hedge ask every question 
about every person,

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and then choose the person with 
only checks and blanks.

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

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have him move on to the next person.

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

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

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Hedge buzzes through the crowd,

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and within minutes finds Adila, 
the resistance leader,

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and brings her back to Ethic.

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

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but under one condition:

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that Ethic and Hedge jump-start 
the revolution

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by reprogramming the furnace-bots 
that terrorize the town.

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And right on cue, the robots descend.