The World Machine | Think Like A Coder, Ep 10

As Ethic falls, she remembers.

She remembers the world before they unearthed the crystal.

She remembers the glee she felt when she built her first robot.

But mostly she remembers the friends she’s made

these last few days:

courageous Adila and her resistance movement.

Octavia’s sacrifice to keep the guards distracted.

Lemma and her idealistic drive to cure everyone.

And Hedge.

Her creation, her responsibility, her failure… her betrayer.

Hedge, who convinced her to collect the three nodes

that she never actually needed.

For Ethic remembers how to operate the World Machine.

If only she could get a second chance at it.

Adila has been in radio contact with Octavia,

whom the robots captured and imprisoned in the same jail that held Ethic.

Ethic explains that Hedge has manipulated them all,

and will now try to break down the Bradbarrier

and cover the entire world in a giant maze,

unless they can stop him.

But she has a plan:

Ethic herself will go to the crystal at the center of the maze

and use its powers to stop Hedge.

Meanwhile, Adila and Lemma will do whatever they can to slow Hedge down.

As Ethic weaves her way towards the innermost maze,

her radio picks up a transmission.

Octavia has freed hundreds of members of the resistance from stasis.

Together, they’ve staged a jailbreak and overwhelmed the guards.

The resistance has access to the World Machine,

but they don’t know how to use it; they’ll need Ethic for that.

All they have at their disposal are nearly limitless spools of wire.

The strands are durable, but prisoners can break them deliberately

if they need to.

Ethic reaches the entrance to the inner most maze… and it’s sealed from within.

She remembers a few things from when she flew over the maze days earlier.

It centers on the crystal.

There are many dead ends, but no paths that loop back on themselves.

Ethic has one opportunity to radio the members of the resistance

a simple set of instructions

before they plunge into the labyrinth in search of the exit.

What directions can she give them so they can quickly navigate the maze,

open the door, and guide Ethic straight back to the crystal?

Pause now to figure it out for yourself.

Hint in 3

Hint in 2

Hint in 1

Here’s a hint:

One of the challenges here is to find a way to indicate where dead ends are,

so that the resistance members don’t keep going down them.

Try simplifying the maze to something like this.

Let’s say you’ve just hit this dead end, then came back to this intersection.

What could you do to show the next person who gets here

that they don’t need to explore that path?

Pause now to figure it out yourself.

Solution in 3

Solution in 2

Solution in 1

Most programming puzzles involve giving instructions to a single actor

so that they can accomplish a goal.

Instead, here we have a swarm of individuals,

each of whom can follow basic instructions.

That’s unusual in programming, but not unheard of;

researchers are currently experimenting with swarms of small robots

to do things like conduct search and rescue missions.

The prisoners aren’t robots, but for Ethic’s purposes they’ll act like them.

And by working together they can achieve their goal much more efficiently.

Because you have a lot of prisoners, you’ll want them to cover a lot of ground.

This matches up well to a maze-mapping technique called a depth-first search.

It’s called that because it involves going as deeply down a path as possible

before going back.

In other words, if you had a maze like this,

you’d want to explore all the way down one of these branches

before returning to this intersection and trying another.

Everyone needs a clear set of instructions for what they should do.

Like — first, tie down the loose end of your wire by the crystal,

so it leads back there.

If you find the door, open it and hand your spool to Ethic.

If you’re in a passageway, keep going until you hit a dead end

or an intersection.

But what happens at either of those places?

If someone encounters a dead end,

they should backtrack to the last intersection.

But they also need to mark it, so no one wastes time and goes back there.

The best tool for that is the wire—

one option is to break both sections that lead down the dead end path,

and tie the spool to the wire that leads back to the crystal.

The broken wires tell everyone else who gets to this intersection

“Don’t go this way.”

They’ll also guarantee the final path will lead straight to the crystal,

rather than visiting dead ends.

Ok, so let’s say someone’s at an intersection.

Now which way should they go?

The first priority is to have everyone cover fresh ground

to minimize doubling up.

So if there’s no wire down a direction, go that way.

If there are multiple choices, choose one at random.

What if they’re in a sub-section like this, with 3 marked dead ends?

The only thing to do is to go back where they came from.

We now know that this whole section is one big dead end,

so they should break and retie the wire when they get to the next intersection.

But let’s say they get there, and find two options where someone’s exploring,

but no one’s hit a dead end yet.

They may as well choose at random and go help explore that path further,

in case it’s the right direction for the exit.

This isn’t the only way to solve this challenge, but in any correct method,

someone will eventually find the way out.

The moment of truth will be when Ethic takes their wire and follows it back,

inward towards her goal.

The great thing about this method is that Ethic’s path is straight and true.

The maze doesn’t have loops, so there's only one path from door to crystal.

And because everyone has been breaking and retying their wires,

Ethic won’t go down any dead-end paths.

Face to face with her creation, Ethic has a choice:

she can destroy Hedge, or set things right.

All of this destruction was her fault, not Hedge’s;

it was her oversight that instructed him to build an infinitely large maze.

His decisions were misguided, but everything he did,

he did to follow his programming.

Ethic accesses his core and fixes her error with a single number:

the size the maze was supposed to reach.

Ethic has prevented catastrophe

and regained possession of the World Machine.

Her work with Adila, Octavia, and Lemma has already started to help people

and heal the world’s turmoil, but there’s much work to be done.

With the forgetting food out of their systems,

the people will become themselves again.

They’ll regain their will to create and progress.

They’ll be free to break down the walls they’ve built between each other.

And they may come to approach their future with a little less greed

and a little more... Ethic