private void DepthFirstTraverse(Digraph <T> digraph, T vertex, HashSet <T> visited)
{
preOrder.Enqueue(vertex);
visited.Add(vertex);
foreach (var neighbour in digraph.GetNeighbours(vertex))
{
if (!visited.Contains(neighbour))
{
DepthFirstTraverse(digraph, neighbour, visited);
}
}
postOrder.Enqueue(vertex);
reversePostOrder.Push(vertex);
}
public DirectedCycle(Digraph <T> digraph)
{
if (digraph == null)
{
throw new ArgumentNullException(nameof(digraph));
}
var currentPath = new HashSet <T>();
var edgeTo = new Dictionary <T, T>();
var visited = new HashSet <T>();
foreach (var vertex in digraph.Vertices)
{
if (!visited.Contains(vertex))
{
DepthFirstTraverse(digraph, vertex, visited, currentPath, edgeTo);
}
}
}
public DepthFirstOrder(Digraph <T> digraph)
{
if (digraph == null)
{
throw new ArgumentNullException(nameof(digraph));
}
postOrder = new Queue <T>(digraph.VertexNumber);
preOrder = new Queue <T>(digraph.VertexNumber);
reversePostOrder = new Stack <T>(digraph.VertexNumber);
var visited = new HashSet <T>();
foreach (var vertex in digraph.Vertices)
{
if (!visited.Contains(vertex))
{
DepthFirstTraverse(digraph, vertex, visited);
}
}
}
public int[] FindOrder(int numCourses, int[][] prerequisites)
{
var courses = new List <int>();
if (prerequisites != null)
{
var digraph = new Digraph <int>();
foreach (var prerequisite in prerequisites)
{
digraph.AddEdge(prerequisite[1], prerequisite[0]);
}
var order = new Topological <int>(digraph).Order;
if (order == null && prerequisites.Length > 0)
{
return(new int[0]);
}
if (order != null)
{
foreach (var course in order)
{
courses.Add(course);
}
}
}
while (numCourses-- > 0)
{
if (!courses.Contains(numCourses))
{
courses.Add(numCourses);
}
}
return(courses.ToArray());
}
