Graphs | Vertex & Graph Data Structures

DIRECTORY.md

@@ -204,7 +204,7 @@
                 * [Directedgraph](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/main/kotlin/com/kotlinground/datastructures/graphs/DirectedGraph.kt)
                 * [Edge](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/main/kotlin/com/kotlinground/datastructures/graphs/Edge.kt)
                 * [Graph](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/main/kotlin/com/kotlinground/datastructures/graphs/Graph.kt)
-                * [Graphnode](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/main/kotlin/com/kotlinground/datastructures/graphs/GraphNode.kt)
+                * [Vertex](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/main/kotlin/com/kotlinground/datastructures/graphs/Vertex.kt)
               * Linkedlists
                 * Doubly
                   * [Doublylinkedlist](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/main/kotlin/com/kotlinground/datastructures/linkedlists/doubly/DoublyLinkedList.kt)
@@ -267,6 +267,8 @@
                   * [Mergeablestateflowimpltest](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/test/kotlin/com/kotlinground/datastructures/crdt/cvrdt/MergeableStateFlowImplTest.kt)
                   * [Mergeablevaluetest](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/test/kotlin/com/kotlinground/datastructures/crdt/cvrdt/MergeableValueTest.kt)
                   * [Utilstest](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/test/kotlin/com/kotlinground/datastructures/crdt/cvrdt/UtilsTest.kt)
+              * Graphs
+                * [Vertextest](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/test/kotlin/com/kotlinground/datastructures/graphs/VertexTest.kt)
               * Linkedlists
                 * Doubly
                   * [Doublylinkedlisttest](https://github.com/BrianLusina/KotlinGround/blob/master/datastructures/src/test/kotlin/com/kotlinground/datastructures/linkedlists/doubly/DoublyLinkedListTest.kt)

datastructures/src/main/kotlin/com/kotlinground/datastructures/graphs/DirectedGraph.kt

@@ -1,5 +1,5 @@
 package com.kotlinground.datastructures.graphs
 
-class DirectedGraph : Graph<GraphNode>() {
+class DirectedGraph<T> : Graph<Vertex<T>>() {
 
 }

datastructures/src/main/kotlin/com/kotlinground/datastructures/graphs/Graph.kt

@@ -1,4 +1,4 @@
 package com.kotlinground.datastructures.graphs
 
 abstract class Graph<Node> {
-}
+}

datastructures/src/main/kotlin/com/kotlinground/datastructures/graphs/Vertex.kt

@@ -0,0 +1,31 @@
+package com.kotlinground.datastructures.graphs
+
+import java.util.UUID
+
+/**
+ * Vertex represents a node in a Graph
+ * @param data [T] Data contained in a vertex
+ * @param id [UUID] ID of the vertex
+ * @param properties [HashMap] Key-value pair of meta information or properties of a vertex
+ */
+data class Vertex<T>(
+    val data: T,
+    val id: String = UUID.randomUUID().toString(),
+    val adjacentVertices: HashMap<String, Vertex<T>> = hashMapOf(),
+    val properties: HashMap<String, Any> = hashMapOf(),
+) {
+
+    /**
+     * Adds an adjacent vertex
+     * @param vertex [Vertex] vertex to add as a neighbour
+     */
+    fun addAdjacentVertex(vertex: Vertex<T>) {
+        if (!adjacentVertices.containsKey(vertex.id.toString())) {
+            // add vertex to adjacent vertices if not available
+            adjacentVertices[vertex.id.toString()] = vertex
+
+            // add this as an adjacent vertex to this vertex
+            vertex.addAdjacentVertex(this)
+        }
+    }
+}

datastructures/src/test/kotlin/com/kotlinground/datastructures/graphs/VertexTest.kt

@@ -0,0 +1,26 @@
+package com.kotlinground.datastructures.graphs
+
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+import java.util.*
+
+class VertexTest {
+    @Test
+    fun `should add adjacent vertex for a vertex`() {
+        val vertexId = UUID.randomUUID().toString()
+        val vertex = Vertex(1, id = vertexId)
+
+        val otherVertexId = UUID.randomUUID().toString()
+        val otherVertex = Vertex(2, id = otherVertexId)
+
+        vertex.addAdjacentVertex(otherVertex)
+
+        val vertexNeighbour = vertex.adjacentVertices[otherVertexId]
+        assertNotNull(vertexNeighbour)
+        assertEquals(otherVertex, vertexNeighbour)
+
+        val otherVertexNeighbour = otherVertex.adjacentVertices[vertexId]
+        assertNotNull(otherVertexNeighbour)
+        assertEquals(vertex, otherVertexNeighbour)
+    }
+}