// Postorder Traversal
bool dfs(int vertex, DirectedGraph graph, Stack <int> order, bool[] visited, bool[] recStack)
{
if (visited[vertex])
{
return(true);
}
visited[vertex] = true;
recStack[vertex] = true;
var adj = graph.GetVertexAdjcency(vertex);
for (int i = 0; i < adj.Count; i++)
{
if (!visited[adj[i]] && !dfs(adj[i], graph, order, visited, recStack))
{
return(false);
}
else if (recStack[adj[i]])
{
return(false);
}
}
order.Push(vertex);
recStack[vertex] = false;
return(true);
}
void FillStronglyConnectedComponent(int vertex, bool[] visited, DirectedGraph graph, StronglyConnectedComponent scc)
{
visited[vertex] = true;
scc.Vertices.Add(vertex);
foreach (var adj in graph.GetVertexAdjcency(vertex))
{
if (!visited[adj])
{
FillStronglyConnectedComponent(adj, visited, graph, scc);
}
}
}
void PostOrder(int vertex, Stack <int> stack, bool[] visited, DirectedGraph graph)
{
visited[vertex] = true;
foreach (var adj in graph.GetVertexAdjcency(vertex))
{
if (!visited[adj])
{
PostOrder(adj, stack, visited, graph);
}
}
stack.Push(vertex);
}
int[] GetIndegrees(DirectedGraph graph)
{
var indegrees = new int[graph.V];
for (int i = 0; i < graph.V; i++)
{
var adj = graph.GetVertexAdjcency(i);
for (int j = 0; j < adj.Count; j++)
{
indegrees[adj[j]]++;
}
}
return(indegrees);
}
protected override void Sort(DirectedGraph graph, ICollection <int> items)
{
var indegrees = GetIndegrees(graph);
var queue = new Queue <int>();
for (int i = 0; i < indegrees.Length; i++)
{
if (indegrees[i] == 0)
{
queue.Enqueue(i);
indegrees[i] = -1;
items.Add(i);
}
}
while (queue.Count > 0)
{
var vertex = queue.Dequeue();
var adj = graph.GetVertexAdjcency(vertex);
for (int i = 0; i < adj.Count; i++)
{
indegrees[adj[i]]--;
if (indegrees[adj[i]] == 0)
{
queue.Enqueue(adj[i]);
items.Add(adj[i]);
}
}
}
if (items.Count != graph.V)
{
items.Clear();
}
}