
/*	findcycle.c

	Identify a cycle in a graph, if one exists.

	begun: March 6, 2002
	by: Steven Skiena
*/

/*
Copyright 2003 by Steven S. Skiena; all rights reserved. 

Permission is granted for use in non-commerical applications
provided this copyright notice remains intact and unchanged.

This program appears in my book:

"Programming Challenges: The Programming Contest Training Manual"
by Steven Skiena and Miguel Revilla, Springer-Verlag, New York 2003.

See our website www.programming-challenges.com for additional information.

This book can be ordered from Amazon.com at

http://www.amazon.com/exec/obidos/ASIN/0387001638/thealgorithmrepo/

*/


#include "bool.h"
#include "graph.h"

extern bool processed[];	/* which vertices have been processed */
extern bool discovered[];	/* which vertices have been found */
extern int parent[];		/* discovery relation */

extern bool finished;		/* flag for early search cutoff */


process_vertex_early(int v)
{
}

process_vertex_late(int v)
{
}

process_edge(int x, int y)
{
	if (parent[x] != y) {	/* found back edge! */
		printf("Cycle from %d to %d:",y,x);
		find_path(y,x,parent);
		printf("\n\n");
		finished = TRUE;
	}
}


main()
{
	graph g;
	int i;

	read_graph(&g,FALSE);
	print_graph(&g);

	initialize_search(&g);
	dfs(&g,1);
}



