public void MinimumSpanningTreePrim(VertexMST <T> root)
{
foreach (var vertex in vertices.OfType <VertexMST <T> >())
{
vertex.Key = int.MaxValue;
vertex.Predecessor = null;
}
root.Key = 0;
var heap = new MinHeap <VertexMST <T> >(vertices.Count, vertices.OfType <VertexMST <T> >().ToArray());
while (!heap.IsEmpty)
{
//had to call heapify before extract min since it's not a min heap anymore due to the change of keys
//instead of decrease key
heap.Heapify(0);
var min = heap.Extract();
foreach (var edge in edges.Where((e) => e.From.Equals(min) || e.To.Equals(min)))
{
if (edge.To.Equals(min))
{
if (heap.Contains(edge.From as VertexMST <T>) &&
edge.Weight < (edge.From as VertexMST <T>).Key)
{
edge.From.Predecessor = min;
(edge.From as VertexMST <T>).Key = edge.Weight;
}
}
else
{
if (heap.Contains(edge.To as VertexMST <T>) &&
edge.Weight < (edge.To as VertexMST <T>).Key)
{
edge.To.Predecessor = min;
(edge.To as VertexMST <T>).Key = edge.Weight;
}
}
}
}
}
//edges' weights cannot be negative
public void Dijkstra(IVertex <T> source)
{
Initialize(source);
//var set = new List<VertexSSSP<T>>();
var heap = new MinHeap <VertexSSSP <T> >(vertices.Count + edges.Count);
heap.Insert(source as VertexSSSP <T>);
while (!heap.IsEmpty)
{
var vertex = heap.Extract();
if (vertex.Visited)
{
continue;
}
vertex.Visited = true;
//set.Add(node.Key);
foreach (var edge in edges.Where((e) => e.From.Equals(vertex)))
{
Relax(edge.From, edge.To, edge.Weight);
heap.Insert(edge.To as VertexSSSP <T>);
}
}
}
