public static void VisitDFS(GraphSuccesorList graph, int v, Stack <int> result, bool[] visited)
{
if (!visited[v])
{
visited[v] = true;
foreach (var child in graph.GetSuccesors(v))
{
VisitDFS(graph, child, result, visited);
}
result.Push(v);
}
}
//public static HashSet<int> TopologicalSortKahn(GraphSuccesorList graph)
//{
// var stack = new Stack<int>();
// var set = new HashSet<int>();
// var topologicallySortedSet = new HashSet<int>();
// // how to implement ? vertex with no incoming edge?
// throw new NotImplementedException();
//}
//public static int TopologicalSortDFSRecursive(GraphSuccesorList graph, HashSet<int> visited, int v)
//{
// var result = 0;
// if (!visited.Contains(v))
// {
// visited.Add(v);
// result = v;
// foreach (var child in graph.GetSuccesors(v))
// {
// TopologicalSortDFSRecursive(graph, visited, v);
// }
// }
// return result;
//}
//public static void TopSortHelpers<T> (int v, bool[] visited, Stack<T> stack)
//{
// visited[v] = true;
//}
public static Stack <int> TopoSort(GraphSuccesorList graph)
{
var visited = new bool[graph.Size()];
var sortedResult = new Stack <int>();
for (int v = 0; v < graph.Size(); v++)
{
//visited[v] = true;
if (!visited[v])
{
VisitDFS(graph, v, sortedResult, visited);
}
}
return(sortedResult);
}
