ConnectedComponents.js

class GraphUnweightedUndirectedAdjacencyList {
 // Unweighted Undirected Graph class
 constructor() {
 this.connections = {}
 }

 addNode(node) {
 // Function to add a node to the graph (connection represented by set)
 this.connections[node] = new Set()
 }

 addEdge(node1, node2) {
 // Function to add an edge (adds the node too if they are not present in the graph)
 if (!(node1 in this.connections)) {
 this.addNode(node1)
 }
 if (!(node2 in this.connections)) {
 this.addNode(node2)
 }
 this.connections[node1].add(node2)
 this.connections[node2].add(node1)
 }

 DFSComponent(components, node, visited) {
 // Helper function to populate the visited set with the nodes in each component

 // adding the first visited node in the component to the array
 components.push(node)
 const stack = [node]
 // populating the visited set using DFS (Iterative)
 while (stack.length > 0) {
 const curr = stack.pop()
 visited.add(curr.toString())
 for (const neighbour of this.connections[curr].keys()) {
 if (!visited.has(neighbour.toString())) {
 stack.push(neighbour)
 }
 }
 }
 }

 connectedComponents() {
 // Function to generate the Connected Components
 // Result is an array containing 1 node from each component
 const visited = new Set()
 const components = []
 for (const node of Object.keys(this.connections)) {
 if (!visited.has(node.toString())) {
 this.DFSComponent(components, node, visited)
 }
 }
 return components
 }
}

export { GraphUnweightedUndirectedAdjacencyList }

// Example

// const graph = new GraphUnweightedUndirectedAdjacencyList()
// graph.addEdge(1, 2) // Component 1
// graph.addEdge(3, 4) // Component 2
// graph.addEdge(3, 5) // Component 2
// const components = graph.connectedComponents()