/** 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 Graph createGraph2() {
Graph graph = new Graph();
KNode n1, n2;
n1 = new KNode("A");
graph.addNode(n1);
n2 = new KNode("B");
graph.addNode(n2);
graph.addEdge(new Edge(n1, n2, 4));
n1 = new KNode("C");
graph.addNode(n1);
n2 = new KNode("D");
graph.addNode(n2);
graph.addEdge(new Edge(n1, n2, 7));
n1 = new KNode("E");
graph.addNode(n1);
n2 = new KNode("F");
graph.addNode(n2);
graph.addEdge(new Edge(n1, n2, 10));
n1 = new KNode("G");
graph.addNode(n1);
n2 = new KNode("H");
graph.addNode(n2);
graph.addEdge(new Edge(n1, n2, 1));
n1 = new KNode("I");
graph.addNode(n1);
graph.addEdge(new Edge((KNode) graph.getNode("B"), (KNode) graph.getNode("C"), 8));
graph.addEdge(new Edge((KNode) graph.getNode("D"), (KNode) graph.getNode("E"), 9));
graph.addEdge(new Edge((KNode) graph.getNode("D"), (KNode) graph.getNode("F"), 14));
graph.addEdge(new Edge((KNode) graph.getNode("C"), (KNode) graph.getNode("F"), 4));
graph.addEdge(new Edge((KNode) graph.getNode("F"), (KNode) graph.getNode("G"), 2));
graph.addEdge(new Edge((KNode) graph.getNode("B"), (KNode) graph.getNode("H"), 11));
graph.addEdge(new Edge((KNode) graph.getNode("H"), (KNode) graph.getNode("A"), 8));
graph.addEdge(new Edge((KNode) graph.getNode("G"), (KNode) graph.getNode("I"), 6));
graph.addEdge(new Edge((KNode) graph.getNode("H"), (KNode) graph.getNode("I"), 7));
graph.addEdge(new Edge((KNode) graph.getNode("C"), (KNode) graph.getNode("I"), 2));
/*
GRAHP:
(B)---8---(C)---7---(D)
/ | / \ | \
4 | 2 \ | 9
/ | / \ | \
(A) 11 (I) 4 14 (E)
\ | / \ \ | /
8 | 7 6 \ | 10
\ | / \ \ | /
(H)---1---(G)---2---(F)
MST:
(B)---8---(C)---7---(D)
/ / \ \
4 2 \ 9
/ / \ \
(A) (I) 4 (E)
\
\
\
(H)---1---(G)---2---(F)
*/
return graph;
}
public Graph createGraph() {
Graph graph = new Graph();
KNode n1, n2;
n1 = new KNode("A");
graph.addNode(n1);
n2 = new KNode("B");
graph.addNode(n2);
graph.addEdge(new Edge(n1, n2, 1));
n1 = new KNode("C");
graph.addNode(n1);
n2 = new KNode("D");
graph.addNode(n2);
graph.addEdge(new Edge(n1, n2, 2));
n1 = new KNode("E");
graph.addNode(n1);
n2 = new KNode("F");
graph.addNode(n2);
graph.addEdge(new Edge(n1, n2, 3));
n1 = new KNode("G");
graph.addNode(n1);
n2 = new KNode("H");
graph.addNode(n2);
graph.addEdge(new Edge(n1, n2, 4));
// box
graph.addEdge(new Edge((KNode) graph.getNode("B"), (KNode) graph.getNode("C"), 5));
graph.addEdge(new Edge((KNode) graph.getNode("D"), (KNode) graph.getNode("E"), 6));
graph.addEdge(new Edge((KNode) graph.getNode("F"), (KNode) graph.getNode("G"), 7));
graph.addEdge(new Edge((KNode) graph.getNode("H"), (KNode) graph.getNode("A"), 8));
// cross
graph.addEdge(new Edge((KNode) graph.getNode("A"), (KNode) graph.getNode("G"), 9));
graph.addEdge(new Edge((KNode) graph.getNode("C"), (KNode) graph.getNode("G"), 10));
graph.addEdge(new Edge((KNode) graph.getNode("C"), (KNode) graph.getNode("E"), 11));
/*
GRAPH:
(A)---1---(B)---5---(C)---2---(D)
| \ / \ |
| \ / \ |
| \ / \ |
8 9 10 11 6
| \ / \ |
| \ / \ |
| \ / \ |
(H)---4---(G)---7---(F)---3---(E)
MST:
(A)---1---(B)---5---(C)---2---(D)
|
|
|
6
|
|
|
(H)---4---(G)---7---(F)---3---(E)
*/
return graph;
}