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Add Boruvka's algorithm to find Minimum Spanning Tree (#4964)
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Niklas Hoefflin
@ -0,0 +1,191 @@
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package com.thealgorithms.datastructures.graphs;
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import static org.junit.jupiter.api.Assertions.*;
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import com.thealgorithms.datastructures.graphs.BoruvkaAlgorithm.Graph;
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import java.util.ArrayList;
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import java.util.List;
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import org.junit.jupiter.api.Test;
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public class BoruvkaAlgorithmTest {
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@Test
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public void testBoruvkaMSTV9E14() {
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List<BoruvkaAlgorithm.Edge> edges = new ArrayList<>();
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edges.add(new BoruvkaAlgorithm.Edge(0, 1, 10));
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edges.add(new BoruvkaAlgorithm.Edge(0, 2, 12));
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edges.add(new BoruvkaAlgorithm.Edge(1, 2, 9));
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edges.add(new BoruvkaAlgorithm.Edge(1, 3, 8));
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edges.add(new BoruvkaAlgorithm.Edge(2, 4, 3));
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edges.add(new BoruvkaAlgorithm.Edge(2, 5, 1));
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edges.add(new BoruvkaAlgorithm.Edge(4, 5, 3));
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edges.add(new BoruvkaAlgorithm.Edge(4, 3, 7));
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edges.add(new BoruvkaAlgorithm.Edge(3, 6, 8));
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edges.add(new BoruvkaAlgorithm.Edge(3, 7, 5));
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edges.add(new BoruvkaAlgorithm.Edge(5, 7, 6));
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edges.add(new BoruvkaAlgorithm.Edge(6, 7, 9));
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edges.add(new BoruvkaAlgorithm.Edge(6, 8, 2));
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edges.add(new BoruvkaAlgorithm.Edge(7, 8, 11));
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final var graph = new Graph(9, edges);
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/**
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* Adjacency matrix
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* 0 1 2 3 4 5 6 7 8
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* 0 0 10 12 0 0 0 0 0 0
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* 1 10 0 9 8 0 0 0 0 0
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* 2 12 9 0 0 3 1 0 0 0
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* 3 0 8 0 0 7 0 8 5 0
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* 4 0 0 3 7 0 3 0 0 0
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* 5 0 0 1 0 3 0 0 6 0
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* 6 0 0 0 8 0 0 0 9 2
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* 7 0 0 0 5 0 6 9 0 11
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* 8 0 0 0 0 0 0 2 11 0
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*/
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final var result = BoruvkaAlgorithm.boruvkaMST(graph);
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assertEquals(8, result.size());
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assertEquals(43, computeTotalWeight(result));
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}
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@Test
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void testBoruvkaMSTV2E1() {
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List<BoruvkaAlgorithm.Edge> edges = new ArrayList<>();
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edges.add(new BoruvkaAlgorithm.Edge(0, 1, 10));
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final var graph = new Graph(2, edges);
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/**
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* Adjacency matrix
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* 0 1
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* 0 0 10
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* 1 10 0
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*/
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final var result = BoruvkaAlgorithm.boruvkaMST(graph);
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assertEquals(1, result.size());
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assertEquals(10, computeTotalWeight(result));
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}
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@Test
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void testCompleteGraphK4() {
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List<BoruvkaAlgorithm.Edge> edges = new ArrayList<>();
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edges.add(new BoruvkaAlgorithm.Edge(0, 1, 7));
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edges.add(new BoruvkaAlgorithm.Edge(0, 2, 2));
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edges.add(new BoruvkaAlgorithm.Edge(0, 3, 5));
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edges.add(new BoruvkaAlgorithm.Edge(1, 2, 3));
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edges.add(new BoruvkaAlgorithm.Edge(1, 3, 4));
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edges.add(new BoruvkaAlgorithm.Edge(2, 3, 1));
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final var graph = new Graph(4, edges);
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/**
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* Adjacency matrix
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* 0 1 2 3
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* 0 0 7 2 5
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* 1 7 0 3 4
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* 2 2 3 0 1
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* 3 5 4 1 0
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*/
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final var result = BoruvkaAlgorithm.boruvkaMST(graph);
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assertEquals(3, result.size());
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assertEquals(6, computeTotalWeight(result));
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}
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@Test
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void testNegativeVertices() {
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Exception exception1 = assertThrows(IllegalArgumentException.class, () -> new Graph(-1, null));
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String expectedMessage = "Number of vertices must be positive";
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String actualMessage = exception1.getMessage();
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assertTrue(actualMessage.contains(expectedMessage));
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}
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@Test
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void testEdgesNull() {
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Exception exception = assertThrows(IllegalArgumentException.class, () -> new Graph(0, null));
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String expectedMessage = "Edges list must not be null or empty";
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String actualMessage = exception.getMessage();
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assertTrue(actualMessage.contains(expectedMessage));
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}
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@Test
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void testEdgesEmpty() {
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Exception exception = assertThrows(IllegalArgumentException.class, () -> new Graph(0, new ArrayList<>()));
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String expectedMessage = "Edges list must not be null or empty";
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String actualMessage = exception.getMessage();
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assertTrue(actualMessage.contains(expectedMessage));
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}
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@Test
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void testEdgesRange() {
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// Valid input
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List<BoruvkaAlgorithm.Edge> validEdges = new ArrayList<>();
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validEdges.add(new BoruvkaAlgorithm.Edge(0, 1, 2));
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validEdges.add(new BoruvkaAlgorithm.Edge(1, 2, 3));
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final var validGraph = new BoruvkaAlgorithm.Graph(3, validEdges);
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assertEquals(validEdges, validGraph.edges);
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// Edge source out of range
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Exception exception1 = assertThrows(IllegalArgumentException.class, () -> {
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List<BoruvkaAlgorithm.Edge> invalidEdges = new ArrayList<>();
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invalidEdges.add(new BoruvkaAlgorithm.Edge(-1, 1, 2));
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final var invalidGraph = new BoruvkaAlgorithm.Graph(1, invalidEdges);
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assertEquals(invalidEdges, invalidGraph.edges);
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});
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String expectedMessage1 = "Edge vertex out of range";
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String actualMessage1 = exception1.getMessage();
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assertTrue(actualMessage1.contains(expectedMessage1));
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// Edge source out of range
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Exception exception2 = assertThrows(IllegalArgumentException.class, () -> {
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List<BoruvkaAlgorithm.Edge> invalidEdges = new ArrayList<>();
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invalidEdges.add(new BoruvkaAlgorithm.Edge(1, 0, 2));
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final var invalidGraph = new BoruvkaAlgorithm.Graph(1, invalidEdges);
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assertEquals(invalidEdges, invalidGraph.edges);
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});
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String expectedMessage2 = "Edge vertex out of range";
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String actualMessage2 = exception2.getMessage();
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assertTrue(actualMessage2.contains(expectedMessage2));
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// Edge destination out of range
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Exception exception3 = assertThrows(IllegalArgumentException.class, () -> {
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List<BoruvkaAlgorithm.Edge> invalidEdges = new ArrayList<>();
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invalidEdges.add(new BoruvkaAlgorithm.Edge(0, -1, 2));
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final var invalidGraph = new BoruvkaAlgorithm.Graph(1, invalidEdges);
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assertEquals(invalidEdges, invalidGraph.edges);
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});
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String expectedMessage3 = "Edge vertex out of range";
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String actualMessage3 = exception3.getMessage();
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assertTrue(actualMessage3.contains(expectedMessage3));
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// Edge destination out of range
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Exception exception4 = assertThrows(IllegalArgumentException.class, () -> {
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List<BoruvkaAlgorithm.Edge> invalidEdges = new ArrayList<>();
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invalidEdges.add(new BoruvkaAlgorithm.Edge(0, 1, 2));
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final var invalidGraph = new BoruvkaAlgorithm.Graph(1, invalidEdges);
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assertEquals(invalidEdges, invalidGraph.edges);
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});
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String expectedMessage4 = "Edge vertex out of range";
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String actualMessage4 = exception4.getMessage();
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assertTrue(actualMessage4.contains(expectedMessage4));
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}
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/**
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* Computes the total weight of the Minimum Spanning Tree
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*
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* @param result list of edges in the Minimum Spanning Tree
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* @return the total weight of the Minimum Spanning Tree
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*/
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int computeTotalWeight(final List<BoruvkaAlgorithm.Edge> result) {
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int totalWeight = 0;
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for (final var edge : result) {
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totalWeight += edge.weight;
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}
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return totalWeight;
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}
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}
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