int DIGRAPHdfs( Digraph G, Vertex r) {
Vertex v;
conta = 0;
for (v = 0; v < G->V; v++) lbl[v] = -1;
dfsR( G, r);
if (conta < G->V) return -1;
return 0;
}
void dfsR( Digraph G, Vertex v) {
Vertex w;
lbl[v] = conta++;
for (w = 0; w < G->V; w++)
if (G->adj[v][w] != 0)
if (lbl[w] == -1)
dfsR( G, w);
}
void dfsR(Graph G, Edge e)
{
link t; int v, w = e.w; Edge x;
if (e.v != e.w)
printf("edge (%d, %d) is tree \n", e.v, e.w) ;
st[e.w] = e.v;
pre[w] = time++;
for (t = G->adj[w]; t != NULL; t = t->next)
if (pre[t->v] == -1)
dfsR(G, EDGE(w, t->v));
else {
v = t->v;
x = EDGE(w, v);
if (pre[w] < pre[v])
printf("edge (%d, %d) is back \n", x.v, x.w) ;
}
post[w] = time++;
}
void GRAPHdfs(Graph G)
{
int v;
time = 0;
for (v=0; v < G->V; v++)
{
pre[v] = -1;
post[v] = -1;
st[v] = -1;
}
for (v=0; v < G->V; v++)
if (pre[v]== -1)
dfsR(G, EDGE(v,v));
printf("discovery/endprocessing time labels \n");
for (v=0; v < G->V; v++)
printf("vertex %d : %d/%d \n", v, pre[v], post[v]);
printf("resulting DFS tree \n");
for (v=0; v < G->V; v++)
printf("parent of vertex %d is vertex %d \n", v, st[v]);
}
