// 先判断有没有回路，有回路再处理
public MSTEdge[] Kruskal()
{
// This will store the resultant MST
MSTEdge[] mst = new MSTEdge[VertexCount - 1];
// Step 1: Sort all the edges in non-decreasing order of their weight
// If we are not allowed to change the given graph, we can create a copy of
// array of edges
var sortedEdges = this.Edges.OrderBy(t => t.Weight);
var enumerator = sortedEdges.GetEnumerator();
// Allocate memory for creating V ssubsets
// Create V subsets with single elements
MSTSubset[] subsets = new MSTSubset[VertexCount];
for (int i = 0; i < subsets.Length; i++)
{
subsets[i] = new MSTSubset();
subsets[i].Parent = i;
subsets[i].Rank = 0;
}
// Number of edges to be taken is equal to V-1
int e = 0;
while (e < VertexCount - 1)
{
// Step 2: Pick the smallest edge. And increment the index
// for next iteration
MSTEdge nextEdge;
if (enumerator.MoveNext())
{
nextEdge = enumerator.Current;
int x = Find(subsets, nextEdge.Begin);
int y = Find(subsets, nextEdge.End);
// If including this edge does't cause cycle, include it
// in result and increment the index of result for next edge
if (x != y)
{
mst[e++] = nextEdge;
Union(subsets, x, y);
}
else
{
// Else discard the nextEdge
}
}
}
return(mst);
}
public bool HasCycle()
{
MSTSubset[] subsets = new MSTSubset[VertexCount];
for (int i = 0; i < subsets.Length; i++)
{
subsets[i] = new MSTSubset();
subsets[i].Parent = i;
subsets[i].Rank = 0;
}
// Iterate through all edges of graph, find subset of both
// vertices of every edge, if both subsets are same,
// then there is cycle in graph.
foreach (var edge in this.Edges)
{
int x = Find(subsets, edge.Begin);
int y = Find(subsets, edge.End);
if (x == y)
{
return(true);
}
Union(subsets, x, y);
}
return(false);
}
