《那些古怪又让人忧心的问题》第83期:走失的人(2)

There's an old puzzle, from before the daysof cell phones, that goes something like this:

在手机出现之前的时代，有一个古老的谜题：

Suppose you're meeting a friend in anAmerican town that neither of you have been to before. You don't have a chanceto plan a meeting place beforehand. Where do you go?

假设你要在一个美国小镇见一个朋友，但你们俩都从来没有去过那里。你们事先也不能约定见面地点，那么你会去小镇上的哪个地方？

The author of the puzzle suggested that thelogical solution would be to go to the town's main post office and wait at themain receiving window, where out-of-town packages arrive. His logic was thatit's the only place that every town in the US has exactly one of, and whicheveryone would know where to find.

这个谜题的作者建议，一个理性的做法是去小镇上的主要邮局，等在主收信窗口，所有来自于小镇之外的邮件都会先到达这个地方。这种方法的逻辑在于这个地点在每个美国小镇中都只有唯一一个，因而所有人都知道它在哪里。

To me, that argument seems a little importantly, it doesn't hold up experimentally. I've asked that questionto a number of people, and none of them suggested the post office. The originalauthor of that puzzle would be waiting in the mailroom alone.

对我来说这个逻辑有点弱。更重要的是，实际上它也不可行。我问了好几个人这个问题，没有一个人建议去邮局等，看来谜题的原作者只能一个人孤零零地等在邮局里了。

Our lost imMortals have it tougher, sincethey don't know anything about the geography of the planet they're on.

情况对于那两个走失的人来说会更艰难，因为他们对于所处的星球的地理信息一无所知。

Following the coastlines seems like asensible move. Most people live near water, and it's much faster to searchalong a line than over a plane. If your guess turns out to be wrong, you won'thave wasted much time compared to having searched the interior first.

沿着海岸线走看上去会是一个合理的方案。绝大多数人口住在水源附近，而且沿着一条线寻找要比在一片区域里寻找更加快速。就算你猜错了，和搜寻内陆所花的时间相比，走一遍海岸线也用不了多少时间。

Walking around the average continent wouldtake about five years, based on typical width-to-coastline-length ratios forEarth land masses.

根据地球上大洲宽度和海岸线长度的比值来推算，沿着海岸线走完一整圈大洲需要约5年时间。

Let's assume you and the other person areon the same continent. If you both walk counterclockwise, you could circleforever without finding each other. That's no good.

不妨假设你和另一个人都在同一个大洲上，如果你们俩都是逆时针搜寻，很有可能你们永远都遇不到对方。真是糟糕。

A different approach would be to make acomplete circle counterclockwise, then flip a coin. If it comes up heads,circle counterclockwise again. If tails, go clockwise. If you're both followingthe same algorithm, this would give you a high probability of meeting within afew circuits.

另一种方法是先逆时针走一圈，然后扔硬币决定下一圈的方向，如果正面朝上，那么继续逆时针走；如果反面朝上，那么就顺时针走。如果你们两个人都遵循这种方法，那么在几圈之内，你们就会有很大几率相遇。

The assumption that you're both using thesame algorithm is probably optimistic. Fortunately, there's a better solution:Be an ant.

寄希望于你们两个都遵循同样的方法可能有点乐观了，但好在还有一种更好的办法，那就是向蚂蚁学习。