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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: Topological Sort Help
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Date: Thu, 08 Feb 2007 20:27:25 +0100
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Date: 2007-02-08T20:27:25+01:00
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isaac2004 writes:
> thank you very much i understand i am not asking for code, just help
> with my implementation, V and E are psuedo variables for an edge and
> a vertex of a graph, how the algorithm is supposed to work is by
> parsing through the entire matrix, and checking for any vertex(V)
> that has no sucessors(ie no children) when one is found, it is
> thrown onto a stack that holds the order of the verrtexs with least
> successors. this loop then continues through until all vertex are
> put on the stack, having a topological sort. a conditional is set if
> there are no vertexes with successors (a cycle) and that is the
> algorithm, thanks for all the, now i juts need to set up a looping
> conditional setup that checks if there are no out edges from a
> vertex. does this sound right?

Yes, that seems about right.  Now, consider how the graph is
represented: G (I, J) is True if and only if there is an edge from I
to J.  Now, write

function Has_Successors (V : in Vertices; In_Graph : in Digraph)
   return Boolean;

and use it within Topological_Sort.

-- 
Ludovic Brenta.