class Graph {

    private val adjList: HashMap<Int, MutableList<Int>> = HashMap()

    // Adds a vertex to the graph

    fun addVertex(vertex: Int) {

        if (!adjList.containsKey(vertex)) adjList[vertex] = mutableListOf()

    }

    // Adds an edge between two vertices

    fun addEdge(v1: Int, v2: Int) {

        adjList[v1]?.add(v2)

        adjList[v2]?.add(v1)  // Since it's an undirected graph

    }

    // Removes a vertex and its associated edges

    fun removeVertex(vertex: Int) {

        while (adjList[vertex]?.isNotEmpty() == true) {

            val adjacentVertex = adjList[vertex]?.first()

            removeEdge(vertex, adjacentVertex!!)

        }

        adjList.remove(vertex)

    }

    // Removes an edge between two vertices

    fun removeEdge(v1: Int, v2: Int) {

        adjList[v1]?.remove(v2)

        adjList[v2]?.remove(v1)

    }

    // Displays the graph

    fun display() {

        for ((vertex, edges) in adjList) {

            println("$vertex -> $edges")

        }

    }

}

​

// client code to test Graph Implementation in Kotlin

fun main() {

    val graph = Graph()

    graph.addVertex(1)

    graph.addVertex(2)

    graph.addVertex(3)

    graph.addVertex(4)

    graph.addEdge(1, 2)

    graph.addEdge(1, 3)

    graph.addEdge(2, 4)

    graph.addEdge(3, 4)

    graph.display()

    graph.removeEdge(2, 4)

    graph.removeVertex(3)

    graph.display()

}

Cannot GET /selam

​