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The good news is that your experimental robo-ants are a success!
好消息是，你的机器蚁实验成功了。
The bad news is that you accidentally just gave them the ability to shoot deadly lasers... and you can't turn it off.
坏消息是，你不小心赋予了它们发射致命激光的能力，却又无法把它关掉。
You have five minutes to stop them before the lasers go online.
你有五分钟的时间在激光系统启动之前制止它们。
Until then, all of your robo-ants will walk inside their habitat at a speed of exactly 1 meter per minute.
在此之前，所有机器蚁会在窝里行走，速度为每分钟一米。
If they bump into each other or hit a dead end, they'll instantly turn around and walk back the way they came.
要是迎面碰上，或者走到了死胡同，它们立刻就会转身，往原来的方向走回去。
When five minutes are up, they'll turn on their lasers, break free, and stream out into the world, carving a path of destruction as they go.
五分钟一到，它们就会启动激光，逃出蚁窝，往外流窜，走到哪里，摧毁哪里。
Your one chance to stop them is to insert the two emergency vacuum nozzles into the habitat and suck the ants up before they break free.
制止它们的唯一机会，就是将两条紧急真空吸嘴插进蚁窝，在蚂蚁逃脱之前把它们吸走。
The nozzles can press into any one location in the habitat through a membrane covering its front side,
吸嘴可以插进蚁窝的任何位置，只需穿破前面的膜就可，
and any ants that walk past will be sucked up and deactivated.
蚂蚁只要经过吸嘴，就会被吸走并且被解除。
You can't move the nozzles once they're placed without leaving a hole that the robo-ants would pour out of, so choosing the right spots will be key.
吸嘴插入蚁窝后就不能再移动，不然会留下洞口，让机器蚁大量涌出，所以，选择正确的位置非常重要。
The habitat is made out of meter-long tubes.
蚁窝由一米长的管制作而成。
When the robots reach an intersection, they will pick randomly whether to go left, right, or forward.
蚂蚁一走到交叉口，就会随机选择往左、往右或往前走。
They only go backward if they hit hit another robo-ant or a dead end.
他们只有在碰到另一只机器蚁或者走到死胡同时才转头。
Unfortunately, there are hundreds of them inside the habitat, and if even one escapes, it'll do a lot of damage.
不幸的是，蚁窝里有数百只蚂蚁，就算只有一只蚂蚁逃脱，它也会造成很大的破坏。
With just less than five minutes remaining, where should you place the 2 vacuum nozzles to suck up all the robo-ants?
现在只剩下少过五分钟，两个真空吸嘴应该插在哪里，才能把所有机器蚂蚁吸掉？
With robo-ants ricocheting all over the habitat, it might seem impossible to stop them before they break free.
机器蚁在蚁窝里到处流窜，趁它们逃脱之前制止它们，好像是不可能的事情。
But this situation is simpler than it seems. Here's why.
但是这个状况比想象中更简单。为什么呢？
Imagine just two robo-ants crawling toward each other.
想象两只机器蚁相向而行。
When they collide, they immediately reverse directions.
它们一碰撞，就会立刻转身。
And what would that sequence of events look like if they crawled past each other instead?
如果它们只是经过彼此的话，情况会怎样呢？
It would look exactly the same before and after their collision, but with their positions swapped.
不管是在碰撞前后都一样，只是两只蚂蚁的位置对调了。
This is true every time a pair of robo-ants meet.
只要有两只机器蚁相遇，情况都一样。
Because the identities of individual ants don't matter, you just need to figure out where you should put the nozzles
个体蚂蚁的身份不重要，所以你只需要找出正确的插吸嘴位置，
to capture any single ant walking without interruption for less than 5 minutes, starting from any point in the habitat.
在少于5分钟的时间内，捕捉到每一只不停行走的蚂蚁，不管它从蚁窝里的什么位置开始行走。
That's much easier to conceptualize and solve.
有了这个概念，问题就更容易解决了。
Placing the nozzles at intersections where three or four tubes meet seems like your best bet
把吸嘴放在三、四条管的交叉口，可能就是最佳选择，
since that's where the robo-ants might otherwise change directions and miss your nozzles.
因为机器蚁可能会在这里换方向，从而躲避了你的吸嘴。
There are only four intersections... which two should you pick?
交叉口只有四个，你该选择哪两个呢？
The top right intersection has to be one of them.
右上方交叉口必须是其中一个。
If it isn't, an ant crawling down from this intersection toward the dead end would crawl for four minutes to get back to the intersection,
要不然，如果蚂蚁从这里走向死胡同，它爬行四分钟后将会回到交叉口，
and then go in any of three directions, walking for at least another minute.
然后从三个方向中选择一个，继续行走至少一分钟。
Once you've placed a nozzle in the top right, the only other choice that has a chance to work is the bottom left.
一旦在右上方插入了吸嘴，就只剩下一个有效的选择，就是左下方交叉口。
To see that this works, imagine an ant anywhere else in the habitat.
为了证明这样有效，想象一下蚁窝内任何位置的一只蚂蚁。
Worst case scenario, the ant would start right next to the vacuum nozzle, marching away from it.
最糟的情况下，蚂蚁从吸嘴旁边开始，背对着吸嘴行走。
But in all those worst cases, the ant would march for at most 4 meters before being sucked up into the vacuum.
但是就算在这些情况下，蚂蚁爬行最多四米后，就会被真空吸走。
No other choice of two intersection points is guaranteed to get all the robo-ants within five minutes.
除了这两个交叉口的组合之外，其它组合都无法保证能在五分钟内吸走所有蚂蚁。
Having vacuumed them all up, you've averted a major crisis.
吸掉了所有蚂蚁，就化解了一次重大危机。
Before you mess with robo-ants again, you'll want to have a robo-anteater ready.
下次再玩机器蚂蚁之前，最好先准备一只机器食蚁兽。
And wouldn't it be cool if it could fly and breathe fire? There's no way that could go wrong!
要是它能飞、能喷火，那该有多酷！这样就不会出问题了！
