Can you solve the virus riddle? - Lisa Winer

翻译人员: 小布 陈 校对人员: Cissy Yun

Your research team has found a prehistoric virus

你的研究团队发现了一种

preserved in the permafrost

被保存在永冻土层的史前病毒，

and isolated it for study.

你们将它分离出来用作研究。

After a late night working,

在一整晚的工作后，

you're just closing up the lab when a sudden earthquake hits

当你正关上实验室的门时， 一个突如其来的地震发生了，

and knocks out the power.

导致电源断了。

As the emergency generators kick in, an alarm confirms your worst fears:

启用紧急电源之后， 一声警报证实了你最惧怕的事：

all the sample vials have broken.

所有的小药瓶样本已被打碎了。

The virus is contained for now,

病毒现在还存留着，

but unless you can destroy it,

但是除非你能销毁它，

the vents will soon open and unleash a deadly airborne plague.

不久排风扇就会打开， 释放出这种通过空气传播的致命病毒。

Without hesitation, you grab your HazMat suit

毫不犹豫，你抓起了你的防护服

and get ready to save the world.

准备去拯救世界。

The lab is a four by four compound of 16 rooms

实验室是由4乘4， 16个房间组成的，

with an entrance on the northwest corner and an exit at the southeast.

西北角有一个入口， 东南角一个出口。

Each room is connected to the adjacent ones by an airlock,

每个房间都与相邻的房间由 气塞连接着，

and the virus has been released in every room except the entrance.

除了入口那间， 病毒已经弥漫到了其他所有房间。

To destroy it, you must enter each contaminated room

想要销毁它， 你必须进入每一个被污染的房间，

and pull its emergency self-destruct switch.

拉下各自的紧急自毁开关。

But there's a catch.

但是这里有个问题

Because the security system is on lockdown,

因为安全系统是处于一级防范禁闭，

once you enter the contaminated room,

一旦你进入了被污染的房间，

you can't exit without activating the switch,

你不开启开关就不能逃出去，

and once you've done so,

一旦你开了开关，

you won't be able to go back in to that room.

你就没法再回到那个房间去。

You start to draw out possible routes on a pad of paper,

你开始在一叠纸上 画出可能的路线，

but nothing seems to get you to the exit

但是似乎找不到一个能够 不错过任何一个房间

without missing at least one room.

就能走到出口的路线。

So how can you destroy the virus in every contaminated room

因此，要怎样才能销毁 每个被污染的房间

and survive to tell the story?

活着逃出来， 再给大家说起这段故事呢？

Pause here if you want to figure it out for yourself.

如果你想自己琢磨的话， 就按一下暂停键。

Answer in: 3

答案即将揭晓：3！

Answer in: 2

2！

Answer in: 1

1！

If your first instinct is to try to graph your possible moves on a grid,

如果你的直觉是尝试在方格上 画出可能的路线的话，

you've got the right idea.

你的想法是对的。

This puzzle is related to the Hamiltonian path problem

这个谜团与汉密尔顿路径有关，

named after the 19th century Irish mathematician William Rowan Hamilton.

它是以19世纪爱尔兰数学家 威廉·汉密尔顿命名的。

The challenge of the path problem

这个路径问题的挑战是

is to find whether a given graph has a Hamiltonian path.

能否在已有图表上 找出一条汉密尔顿路径。

That's a route that visits every point within it exactly once.

这是一条要求在每个点上 正好划过一次的路线。

This type of problem, classified as NP-complete,

这种类型的问题， 被归类为NP完全问题，

is notoriously difficult when the graph is sufficiently large.

众所周知，当图表足够大时， 这问题奇难无比。

Although any proposed solution can be easily verified,

虽然任何提出的解决方法 都可以被轻易证实，

we have no reliable formula or shortcut for finding one,

我们没有可靠的方程式或捷径 来找出这个方法，

or determining that one exists.

或证明这个方法存在。

And we're not even sure if it's possible for computers

我们甚至也不确定能否依赖计算机

to reliably find such solutions, either.

来可靠地找出这种解决方法。

This puzzle adds a twist to the Hamiltonian path problem

这个难题又将汉密尔顿路径问题 提升了一个难度,

in that you have to start and end at specific points.

因为你要在一个特定的点开始， 并在另一个特定的点结束。

But before you waste a ton of graph paper,

但是在浪费你无数的稿纸之前，

you should know that a true Hamiltonian path

你应该知道真正的汉密尔顿路径

isn't possible with these end points.

若用这些开始或结束的点， 是无法成立的。

That's because the rooms form a grid with an even number of rooms on each side.

那是因为房间形成一个表格， 每边房间的数量都是偶数。

In any grid with that configuration,

在任何一个这样结构的表格里，

a Hamiltonian path that starts and ends in opposite corners is impossible.

找出一条起点和终点在相反角落的 汉密尔顿路径是不可能的。

Here's one way of understanding why.

这有一个解释。

Consider a checkerboard grid with an even number of squares on each side.

比如说一个棋盘两边 都有一个偶数量的正方格，

Every path through it will alternate black and white.

通过它的每条路径都会黑白交替。

These grids will all also have an even total number of squares

这些方格的总数量将是偶数，

because an even number times and even number is even.

因为偶数与偶数的积是偶数。

So a Hamiltonian path on an even-sided grid that starts on black

因此在一个偶数边表格上， 汉密尔顿路径若是从黑色方格开始，

will have to end on white.

最终将在白色方格结束。

And one that starts on white will have to end on black.

若是以白色方格开始的话， 就会以黑色方格结束。

However, in any grid with even numbered sides,

但是，在任何偶数边表格中，

opposite corners are the same color,

对角的颜色是相同的，

so it's impossible to start and end a Hamiltonian path on opposite corners.

要找到一个起点和终点在对角的 汉密尔顿路径是不可能的。

It seems like you're out of luck,

似乎你已经没辙了，

unless you look at the rules carefully and notice an important exception.

但是如果你仔细看一下规则， 可以注意到一个很重要的例外。

It's true that once you activate the switch in a contaminated room,

没错，一旦你启动污染房间的开关，

it's destroyed and you can never go back.

它已自毁并且你再也没法回去了。

But there's one room that wasn't contaminated - the entrance.

但有一个房间是没有被污染的， 就是入口的房间。

This means that you can leave it once without pulling the switch

这意味着你可以在 不启动开关的情况下离开一次，

and return there when you've destroyed either of these two rooms.

在你销毁与它相邻的两个房间 其中之一后，再回到入口房间。

The corner room may have been contaminated

角落的房间可能已经 因开着的气塞而被污染了,

from the airlock opening, but that's okay

但这没问题,

because you can destroy the entrance after your second visit.

因为你可以在第二次进入之后 再销毁入口房间。

That return trip gives you four options for a successful route,

重返路线给你提供了 四条可行的路线，

and a similar set of options if you destroyed this room first.

如果你先销毁这个房间的话， 也会出现四类似的方案。

Congratulations. You've prevented an epidemic of apocalyptic proportions,

恭喜，你已经阻止了一个能导致 世界末日的传染病，

but after such a stressful episode, you need a break.

渡过这一难关之后， 你需要休息一下。

Maybe you should take up that recent job offer to become a traveling salesman.

或许你应该答应那个工作机会， 去做一名旅行推销员。