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MSTKruskal.java
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MSTKruskal.java
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/*
* Copyright 2020 Emory University
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package edu.emory.cs.graph.span;
import edu.emory.cs.graph.Edge;
import edu.emory.cs.graph.Graph;
import edu.emory.cs.set.DisjointSet;
import java.util.PriorityQueue;
/** @author Jinho D. Choi ({@code jinho.choi@emory.edu}) */
public class MSTKruskal implements MST {
@Override
public SpanningTree getMinimumSpanningTree(Graph graph) {
PriorityQueue<Edge> queue = new PriorityQueue<>(graph.getAllEdges());
DisjointSet forest = new DisjointSet(graph.size());
SpanningTree tree = new SpanningTree();
while (!queue.isEmpty()) {
Edge edge = queue.poll();
if (!forest.inSameSet(edge.getTarget(), edge.getSource())) {
tree.addEdge(edge);
// a spanning tree is found
if (tree.size() + 1 == graph.size()) break;
// merge forests
forest.union(edge.getTarget(), edge.getSource());
}
}
return tree;
}
}