/** Does not handle Graphs of 1 or fewer nodes */
public Graph kruskal(Graph g) {
boolean add = false;
Graph mst = new Graph(); // initialize graph
Vector edges = g.getEdges(); // get edges
Collections.sort(edges); // sort edges
// find mst
for (int i = 0; i < edges.size(); ++i) {
Edge edge = (Edge) edges.get(i); // get edge
KNode[] ends = edge.getEnds(); // get ends
if (!mst.containsNode(ends[0])) {
mst.addNode(ends[0]); // check for first end
add = true;
}
if (!mst.containsNode(ends[1])) {
mst.addNode(ends[1]); // check other end
add = true;
}
if (add) // if either end is new add edge
{
mst.addEdge(edge);
add = false;
} else // ensure trees are connected if nodes are contained
{
if (!mst.pathBetween(ends)) mst.addEdge(edge);
}
}
return mst;
}
public int compareTo(Object o2) {
Edge e2 = (Edge) o2;
if (this.getWeight() < e2.getWeight()) return -1;
else if (this.getWeight() > e2.getWeight()) return 1;
else if (this.getWeight() == e2.getWeight()) return 0;
return -2;
}
public String printEdges(KNode n) {
Vector edgeSet = new Vector();
for (int i = 0; i < edges.size(); ++i) {
if (((Edge) edges.get(i)).connectsNode(n)) edgeSet.add((Edge) edges.get(i));
}
if (edgeSet.size() == 0) return "-none-";
String value = "";
for (int i = 0; i < edgeSet.size(); ++i) {
Edge e = (Edge) edgeSet.get(i);
value += n + "" + e + "" + e.otherEnd(n) + "\n";
}
return value;
}