diff --git a/core-java/src/main/java/com/baeldung/graph/Graph.java b/core-java/src/main/java/com/baeldung/graph/Graph.java new file mode 100644 index 0000000000..43b5c0aa08 --- /dev/null +++ b/core-java/src/main/java/com/baeldung/graph/Graph.java @@ -0,0 +1,76 @@ +package com.baeldung.graph; + +import java.util.ArrayList; +import java.util.HashMap; +import java.util.List; +import java.util.Map; +import java.util.stream.Collectors; + +public class Graph { + private Map> adjVertices; + + Graph() { + this.adjVertices = new HashMap>(); + } + + void addVertex(String label) { + adjVertices.putIfAbsent(new Vertex(label), new ArrayList<>()); + } + + void removeVertex(String label) { + Vertex v = new Vertex(label); + adjVertices.values().stream().map(e -> e.remove(v)).collect(Collectors.toList()); + adjVertices.remove(new Vertex(label)); + } + + void addEdge(String label1, String label2) { + Vertex v1 = new Vertex(label1); + Vertex v2 = new Vertex(label2); + adjVertices.get(v1).add(v2); + adjVertices.get(v2).add(v1); + } + + void removeEdge(String label1, String label2) { + Vertex v1 = new Vertex(label1); + Vertex v2 = new Vertex(label2); + List eV1 = adjVertices.get(v1); + List eV2 = adjVertices.get(v2); + if (eV1 != null) + eV1.remove(v2); + if (eV2 != null) + eV2.remove(v1); + } + + List getAdjVertices(String label) { + return adjVertices.get(new Vertex(label)); + } + + String printGraph() { + StringBuffer sb = new StringBuffer(); + for(Vertex v : adjVertices.keySet()) { + sb.append(v); + sb.append(adjVertices.get(v)); + } + return sb.toString(); + } + + class Vertex { + String label; + Vertex(String label) { + this.label = label; + } + @Override + public boolean equals(Object obj) { + Vertex vertex = (Vertex) obj; + return vertex.label == label; + } + @Override + public int hashCode() { + return label.hashCode(); + } + @Override + public String toString() { + return label; + } + } +} \ No newline at end of file diff --git a/core-java/src/main/java/com/baeldung/graph/GraphTraversal.java b/core-java/src/main/java/com/baeldung/graph/GraphTraversal.java new file mode 100644 index 0000000000..479e653a5c --- /dev/null +++ b/core-java/src/main/java/com/baeldung/graph/GraphTraversal.java @@ -0,0 +1,44 @@ +package com.baeldung.graph; + +import java.util.LinkedHashSet; +import java.util.LinkedList; +import java.util.Queue; +import java.util.Set; +import java.util.Stack; + +import com.baeldung.graph.Graph.Vertex; + +public class GraphTraversal { + static Set depthFirstTraversal(Graph graph, String root) { + Set visited = new LinkedHashSet(); + Stack stack = new Stack(); + stack.push(root); + while (!stack.isEmpty()) { + String vertex = stack.pop(); + if (!visited.contains(vertex)) { + visited.add(vertex); + for (Vertex v : graph.getAdjVertices(vertex)) { + stack.push(v.label); + } + } + } + return visited; + } + + static Set breadthFirstTraversal(Graph graph, String root) { + Set visited = new LinkedHashSet(); + Queue queue = new LinkedList(); + queue.add(root); + visited.add(root); + while (!queue.isEmpty()) { + String vertex = queue.poll(); + for (Vertex v : graph.getAdjVertices(vertex)) { + if (!visited.contains(v.label)) { + visited.add(v.label); + queue.add(v.label); + } + } + } + return visited; + } +} \ No newline at end of file diff --git a/core-java/src/test/java/com/baeldung/graph/GraphTraversalUnitTest.java b/core-java/src/test/java/com/baeldung/graph/GraphTraversalUnitTest.java new file mode 100644 index 0000000000..d955d56d95 --- /dev/null +++ b/core-java/src/test/java/com/baeldung/graph/GraphTraversalUnitTest.java @@ -0,0 +1,36 @@ +package com.baeldung.graph; + +import org.junit.Assert; +import org.junit.Test; + +public class GraphTraversalUnitTest { + @Test + public void givenAGraph_whenTraversingDepthFirst_thenExpectedResult() { + Graph graph = createGraph(); + Assert.assertEquals("[Bob, Rob, Maria, Alice, Mark]", + GraphTraversal.depthFirstTraversal(graph, "Bob").toString()); + } + + @Test + public void givenAGraph_whenTraversingBreadthFirst_thenExpectedResult() { + Graph graph = createGraph(); + Assert.assertEquals("[Bob, Alice, Rob, Mark, Maria]", + GraphTraversal.breadthFirstTraversal(graph, "Bob").toString()); + } + + Graph createGraph() { + Graph graph = new Graph(); + graph.addVertex("Bob"); + graph.addVertex("Alice"); + graph.addVertex("Mark"); + graph.addVertex("Rob"); + graph.addVertex("Maria"); + graph.addEdge("Bob", "Alice"); + graph.addEdge("Bob", "Rob"); + graph.addEdge("Alice", "Mark"); + graph.addEdge("Rob", "Mark"); + graph.addEdge("Alice", "Maria"); + graph.addEdge("Rob", "Maria"); + return graph; + } +} \ No newline at end of file