/*-------------------Kruskal's Algorithm------------------------------*/
public List <Edge <T> > MSTKruskal()
{
List <Edge <T> > edges = GetEdges(); // get a list of edges
edges.Sort((a, b) => a.Weight.CompareTo(b.Weight)); // sort ascending by weight
Queue <Edge <T> > queue = new Queue <Edge <T> >(edges); // edges instances are queued in new queue
Subset <T>[] subsets = new Subset <T> [Nodes.Count]; // Each node is added to it's own subset. subsets check if addition of edge causes creation of cycle
for (int i = 0; i < Nodes.Count; i++)
{
subsets[i] = new Subset <T>()
{
Parent = Nodes[i]
};
}
List <Edge <T> > result = new List <Edge <T> >(); // store list of edges
while (result.Count < Nodes.Count - 1) // iterates until the correct number of edges found
{
Edge <T> edge = queue.Dequeue(); // get edge with min weight
Node <T> from = GetRoot(subsets, edge.From);
Node <T> to = GetRoot(subsets, edge.To);
if (from != to) // check if no other cycles were introduced
{
result.Add(edge);
Union(subsets, from, to); // union two subsets
}
}
return(result);
}
public static Graph KruskalSolve(Graph graph)
{
int verticesCount = graph.VerticesCount;
Edge[] edgesArray = new Edge[verticesCount];
Array.Sort(graph.Edges, (Edge a, Edge b) =>
{
return(a.Weight.CompareTo(b.Weight));
});
Subset[] subsets = new Subset[verticesCount];
for (int v = 0; v < verticesCount; v++)
{
subsets[v] = new Subset()
{
Parent = v, Rank = 0
}
}
;
int e = default;
int i = default;
while (e < verticesCount - 1)
{
Edge nextEdge = graph.Edges[i++];
int x = Find(subsets, nextEdge.Source);
int y = Find(subsets, nextEdge.Destination);
if (x != y)
{
if (nextEdge != null)
{
edgesArray[e++] = nextEdge;
}
Union(subsets, x, y);
}
}
return(new Graph
{
VerticesCount = verticesCount,
Edges = edgesArray,
EdgesCount = e,
});
}
}
