四个人有过在谁十字架，一个或两个人night.Any方的桥梁，必须携带手电筒他们。手电筒必须来回走着;它不能被抛出，等。每个人行走以不同的速度。一需要1分钟交叉，再过2分钟，另外5，并在最后10分钟。如果两个人交叉在一起，它们必须走在较慢的人的步伐。有没有窍门 - 男人都开始在同一侧，手电筒不亮很长的距离，没有人可以进行等

Four men have to cross a bridge at night.Any party who crosses, either one or two men, must carry the flashlight with them. The flashlight must be walked back and forth; it cannot be thrown, etc. Each man walks at a different speed. One takes 1 minute to cross, another 2 minutes, another 5, and the last 10 minutes. If two men cross together, they must walk at the slower man's pace. There are no tricks--the men all start on the same side, the flashlight cannot shine a long distance, no one can be carried, etc.

和问题是什么是最快的，他们都可以得到跨越。我基本上找一些通用的方式来处理这类问题。有人告诉我，我的朋友，这可以通过斐波那契数列来解决，但解决方案并不适用于所有的工作。

And the question is What's the fastest they can all get across. I am basically looking for some generalized approach to these kind of problem. I was told by my friend, that this can be solved by Fibonacci series, but the solution does not work for all.

请注意，这不是一个家庭的工作。

Please note this is not a home work.

推荐答案

有一个完整的PDF （的备用链路），解决这个问题的一般情况（在正式的证明）。

There is an entire PDF (alternate link) that solves the general case of this problem (in a formal proof).