即使长路径算法-DFS [英] Even length path algorithm -DFS
本文介绍了即使长路径算法-DFS的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
首先,我不会说谎。这是我的家庭作业。我特林解决这一问题太多小时,我不知道。
First, I won't lie. This is my homework. I'm tring to solve this question for too many hours and I have no clue.
我需要写算法(效率)的找到所有与偶数路径长度从给定的顶点到所有其他顶点顶点。
I need to write algorithm ( efficient) that find all the vertices with a even-length path from a given vertex to all other vertices.
我知道它可能是一些与DFS使用...
I know its probably something with DFS uses...
请给我一些指导!
推荐答案
既然是家庭作业,我只是提供了一些提示:
Since it is homework, I am only providing some hints:
- 如果你做一个DFS达到一定的深度,不维护一个
访问
设置 - 所有的顶点,你发现具有路径从源头,长度等于当前深度。 - 如果你做一个DFS高达深度
2 | V |
,所有从源头甚至长路径的顶点将被发现在有的甚至深度级别。 [说服自己为什么:奇数长周期发生了什么?即使长周期发生了什么?]
- If you do a DFS up to a certain depth, without maintaining a
visited
set - all the vertices you "discover" has path from the source, with length equals to the current depth. - If you do a DFS up to depth
2|V|
, all the vertices with even-length paths from the source will be discovered in some even depth level. [convince yourself why: what happens for odd-length cycle? what happens for even-length cycle?]
当心:运行时间是指数的顶点数量[一倍]
Beware: running time is exponential in the number of vertices [doubled].
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