《那些古怪又讓人憂心的問題》第83期:走失的人(2)

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

在手機出現之前的時代，有一個古老的謎題：

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?

假設你要在一個美國小鎮見一個朋友，但你們倆都從來沒有去過那裏。你們事先也不能約定見面地點，那麼你會去小鎮上的哪個地方？

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.

這個謎題的作者建議，一個理性的做法是去小鎮上的主要郵局，等在主收信窗口，所有來自於小鎮之外的郵件都會先到達這個地方。這種方法的邏輯在於這個地點在每個美國小鎮中都只有唯一一個，因而所有人都知道它在哪裏。

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.

對我來說這個邏輯有點弱。更重要的是，實際上它也不可行。我問了好幾個人這個問題，沒有一個人建議去郵局等，看來謎題的原作者只能一個人孤零零地等在郵局裏了。

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

情況對於那兩個走失的人來說會更艱難，因爲他們對於所處的星球的地理信息一無所知。

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.

沿着海岸線走看上去會是一個合理的方案。絕大多數人口住在水源附近，而且沿着一條線尋找要比在一片區域裏尋找更加快速。就算你猜錯了，和搜尋內陸所花的時間相比，走一遍海岸線也用不了多少時間。

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

根據地球上大洲寬度和海岸線長度的比值來推算，沿着海岸線走完一整圈大洲需要約5年時間。

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.

不妨假設你和另一個人都在同一個大洲上，如果你們倆都是逆時針搜尋，很有可能你們永遠都遇不到對方。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.

另一種方法是先逆時針走一圈，然後扔硬幣決定下一圈的方向，如果正面朝上，那麼繼續逆時針走；如果反面朝上，那麼就順時針走。如果你們兩個人都遵循這種方法，那麼在幾圈之內，你們就會有很大機率相遇。

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

寄希望於你們兩個都遵循同樣的方法可能有點樂觀了，但好在還有一種更好的辦法，那就是向螞蟻學習。