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package org.psjava.algo.graph.mst;

import java.util.Comparator;

import org.psjava.algo.graph.NumberOfConnectedComponents;
import org.psjava.algo.sequence.sort.SortingAlgorithm;
import org.psjava.ds.Collection;
import org.psjava.ds.array.DynamicArray;
import org.psjava.ds.array.MutableArray;
import org.psjava.ds.array.MutableArrayFromIterable;
import org.psjava.ds.graph.AllEdgeInGraph;
import org.psjava.ds.graph.Graph;
import org.psjava.ds.graph.UndirectedWeightedEdge;
import org.psjava.ds.numbersystrem.AddableNumberSystem;
import org.psjava.ds.set.DisjointSet;
import org.psjava.ds.set.MakeSetAll;
import org.psjava.goods.GoodDisjointSet;
import org.psjava.util.AssertStatus;

public class KruscalAlgorithm {

	public static MinimumSpanningTreeAlgorithm getInstance(final SortingAlgorithm sort) {
		return new MinimumSpanningTreeAlgorithm() {
			@Override
			public > Collection calc(Graph graph, final AddableNumberSystem ns) {
				AssertStatus.assertTrue(NumberOfConnectedComponents.calc(graph) <= 1);

				MutableArray edges = MutableArrayFromIterable.create(AllEdgeInGraph.wrap(graph));

				sort.sort(edges, new Comparator() {
					@Override
					public int compare(E e1, E r2) {
						return ns.compare(e1.weight(), r2.weight());
					}
				});

				DisjointSet dset = GoodDisjointSet.create();
				MakeSetAll.make(dset, graph.getVertices());

				DynamicArray result = DynamicArray.create();
				for (E e : edges) {
					if (dset.find(e.v1()) != dset.find(e.v2())) {
						result.addToLast(e);
						dset.union(e.v1(), e.v2());
					}
				}
				return result;
			}
		};
	}

	private KruscalAlgorithm() {
	}
}