Re: [Boost-users] Dijkstra example

Subject: Re: [Boost-users] Dijkstra example
From: Cedric Laczny (cedric.laczny_at_[hidden])
Date: 2011-06-07 03:19:58

Hi,

On Tuesday, 7. June 2011 00:32:33 David Doria wrote:
> I tried to modify this example:
> 
> http://www.boost.org/doc/libs/1_34_0/libs/graph/example/dijkstra-example.cp
> p
> 
> to create the graph in a clearer fashion:
> http://codepad.org/DDKs45oe
> 
> However, I now get compiler errors inside dijkstra_shortest_paths.hpp
> 
> Can anyone see where I have gone wrong?

Was not yet able to look at it.

> 
> Also, I don't really understand the "distances and parents" output - I
> just want to know the shortest path between two vertices. In fact I
> don't even see the start and end vertices specified in the original
> example?

You should perhaps have a look at the description of this function of the 
boost-library again, where it says:
Dijkstra's algorithm finds all the shortest paths from the source vertex to 
every other vertex by iteratively ``growing'' the set of vertices S to which 
it knows the shortest path.
s. 
http://www.boost.org/doc/libs/1_34_0/libs/graph/doc/dijkstra_shortest_paths.html

This basically means that you only need to specify the source vertex (called 
"s" in the example), and no end vertex.
To get your shortest path, you would simply start with your end-vertex of 
choice, go to is predecessor, to the predecessor of the predecessor and so on 
until you find your start-vertex (this is called backtracking, IIRC). Here 
again, I would suggest you to read the documentation again (s. above)

> 
> Thanks,
> 
> David
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users

Hope that helps.

Best,

Cedric