DFS Walk optimized

PAL Algoritmus

input: Graph G. output: array p pointing to predecessor vertex, array d with times of vertex opening and array f with time of vertex closing

procedure DFS-Walk(Vertex u) { 
	state[u] = OPEN;
	for each Vertex v in succ(u) 
		if (state[v] == UNVISITED) then {
			DFS-Walk(v ); 
		}
	state[u ] = CLOSED;
} 

DFS-Walk-push(Vertex u) {
	state[u] = OPEN; 
	d[u] = ++time;
	for each Vertex v in succ(u)
		if (state[v ] == UNVISITED) then {
			p[v] = u; 
			DFS-Walk-push(v); 
		}
	state[u] = CLOSED; 
	f[u] = ++time; 
	push u to S;
}