Can you solve the killer robo-ants riddle? - Dan Finkel

譯者: Lilian Chiu 審譯者: Helen Chang

The good news is that your experimental robo-ants

好消息是，你的實驗性 機器螞蟻非常成功！

are a success!

The bad news is that you accidentally

壞消息是，你不小心

just gave them the ability to shoot deadly lasers

給了它們發射致命雷射的能力……

…and you can’t turn it off.

且你無法把它關掉。

You have five minutes to stop them

你有五分鐘可以阻止它們，

before the lasers go online.

然後雷射就會連線。

Until then,

all of your robo-ants will walk

在那之前，你所有的機器螞蟻

inside their habitat at a speed of

都會在它們的棲息地裡行走，

exactly 1 meter per minute.

速度剛好是每分鐘一公尺。

If they bump into each other or hit a dead end,

如果它們撞到或是碰到死路，

they’ll instantly turn around

它們會馬上回轉，從原路走回去。

and walk back the way they came.

When five minutes are up,

五分鐘過後，它們就會啟動雷射，

they’ll turn on their lasers,

break free,

脫身獲得自由，湧入世界中，

and stream out into the world,

carving a path of destruction as they go.

所經之處都會造成毀滅。

Your one chance to stop them is to insert

你有一個機會阻止它們，

就是把兩個緊急用 真空吸塵器的管嘴插入棲息地中，

the two emergency vacuum nozzles into the habitat

and suck the ants up before they break free.

在螞蟻脫身之前把它們吸光。

The nozzles can press into any one location

用力壓管嘴，就可以讓它 穿過棲息地前面的覆蓋薄膜，

in the habitat through a membrane covering

進入棲息地中的任何一處。

its front side, and any ants that walk past

任何經過的螞蟻

will be sucked up and deactivated.

都會被吸起來並停止運作。

You can’t move the nozzles once they’re placed

管嘴放好之後就無法再移動，

without leaving a hole that the robo-ants

一移動就會留下一個洞 讓機器螞蟻逃出來，

would pour out of, so choosing the

right spots will be key.

所以關鍵是要選擇正確的插入點。

The habitat is made out of meter-long tubes.

棲息地是用一公尺長的 管子做成的。

When the robots reach an intersection,

當機器螞蟻到了交叉口時，

they will pick randomly whether to go

它們會隨機選擇要 左轉、右轉，或直走。

left, right, or forward.

They only go backward if they hit

會回轉的情況只有撞到

hit another robo-ant or a dead end.

另一隻機器螞蟻或是碰到死路。

Unfortunately, there are hundreds of them

不幸的是，在棲息地中 有數百隻螞蟻，

inside the habitat, and if even one escapes,

只要有一隻逃脫， 就會造成很大的傷害。

it’ll do a lot of damage.

With just less than five minutes remaining,

只剩下不到五分鐘，

where should you place the 2 vacuum nozzles

你應該要把這兩個真空 吸塵器的管嘴放在哪裡

to suck up all the robo-ants?

才能把所有機器螞蟻都吸起來？

Pause the video now if you want to figure it out for yourself.

Answer in: 3

Answer in: 2

Answer in: 1

With robo-ants ricocheting all over the habitat,

機器螞蟻在棲息地中到處跑，

it might seem impossible to stop them

看起來似乎無法在它們 逃出去之前阻止它們。

before they break free.

But this situation is simpler than it seems.

但這個情況其實 比看起來的還容易解決。

Here's why.

原因如下。

Imagine just two robo-ants crawling

想像只有兩隻機器螞蟻， 它們在爬向彼此。

toward each other.

When they collide, they immediately

當它們相撞時，它們 馬上就會轉向反方向。

reverse directions.

And what would that sequence of events look

如果它們改成是爬過彼此，

like if they crawled past each other instead?

那一連串事件 看起來會是什麼樣子？

It would look exactly the same before

在它們相撞之前和之後

and after their collision, but with

看起來會完全一樣，

their positions swapped.

但它們位置會互換。

This is true every time a pair of robo-ants meet.

每當有一對螞蟻相碰時都是如此。

Because the identities of individual ants

因為每一隻螞蟻的 個別身分並不重要，

don’t matter, you just need to figure out where

你只需要想出你要把管嘴放在哪裡

you should put the nozzles to capture

才能捕捉到每一隻螞蟻，

any single ant walking without interruption

且每隻螞蟻都會從 棲息地的任何地方

for less than 5 minutes, starting from

開始不間斷地行走 不到五分鐘的時間。

any point in the habitat.

That’s much easier to conceptualize and solve.

這樣就比較容易概念化和解題了。

Placing the nozzles at intersections where

把管嘴放在三或四根管子的交叉口

three or four tubes meet seems like your best bet

似乎是最有勝算的選擇，

since that’s where the robo-ants might otherwise

因為若不放在那裡， 機器螞蟻可能會改變方向，

change directions and miss your nozzles.

錯過你的管嘴。

There are only four intersections…

只有四個交叉口……

which two should you pick?

你會挑哪兩個？

The top right intersection has to be one of them.

一定得選右上的交叉口。

If it isn’t, an ant crawling down from

如果沒有選它，當一隻螞蟻 從這個交叉口向下爬，

this intersection toward the dead end would

到達死路之後，

crawl for four minutes to get back to the

就會花四分鐘爬回到這個交叉點，

intersection, and then go in any of three

接著往另外三個方向之一前進，

directions, walking for at least another minute.

再走至少一分鐘。

Once you’ve placed a nozzle in the top right,

當你把一隻管嘴放在右上之後，

the only other choice that has a chance

唯一有可能的選擇就是左下角了。

to work is the bottom left.

To see that this works, imagine an ant

若想知道它如何運作，

想像在棲息地中的任何 其他一處有一隻螞蟻。

anywhere else in the habitat.

Worst case scenario, the ant would start

最糟糕的狀況，這隻螞蟻 會從管嘴旁邊的點開始

right next to the vacuum nozzle, marching away from it.

朝遠離管嘴的方向爬。

But in all those worst cases, the ant would march

但在所有最糟的情況下，

螞蟻最多只能爬四公尺

for at most 4 meters before being sucked

就會被吸到真空吸塵器中。

up into the vacuum.

No other choice of two intersection points

只有選這兩個交叉點，

is guaranteed to get all the robo-ants

才能保證在五分鐘內

抓到所有的機器螞蟻。

within five minutes.

Having vacuumed them all up, you’ve

把它們通通吸掉之後，

averted a major crisis.

你阻止了一項重大危機。

Before you mess with robo-ants again,

在你下次要亂搞機器螞蟻之前，

you’ll want to have a robo-anteater ready.

你會想要把機器食蟻獸先準備好。

And wouldn’t it be cool if it could

如果它還能飛行 和噴火，不是很酷嗎？

fly and breathe fire?

There’s no way that could go wrong!

那不可能會出錯的！