/* topsort1.c
Topologically sort a directed acyclic graph by DFS numbering (DAG)
by: Steven Skiena
begun: March 26, 2002
*/
/*
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"
#include "stack.h"
stack sorted; /* topological ordering of vertices */
extern bool processed[]; /* which vertices have been processed */
extern bool discovered[]; /* which vertices have been found */
extern int parent[]; /* discovery relation */
extern int entry_time[]; /* time of vertex entry */
extern int exit_time[]; /* time of vertex exit */
process_vertex_early(int v)
{
}
process_vertex_late(int v)
{
push(&sorted,v);
}
process_edge(int x, int y)
{
int class; /* edge class */
class = edge_classification(x,y);
if (class == BACK)
printf("Warning: directed cycle found, not a DAG\n");
}
topsort(graph *g)
{
int i; /* counter */
init_stack(&sorted);
for (i=1; i<=g->nvertices; i++)
if (discovered[i] == FALSE)
dfs(g,i);
print_stack(&sorted); /* report topological order */
}
main()
{
graph g;
read_graph(&g,TRUE);
print_graph(&g);
topsort(&g);
}