From 5bd960267504227eff583ae432fe0032a593eca7 Mon Sep 17 00:00:00 2001
From: Tapajyoti Bose <ruppysuppy@gmail.com>
Date: Tue, 7 Jul 2020 11:23:04 +0530
Subject: [PATCH] Added Connected Components using DFS

---
 Graphs/ConnectedComponents.js | 56 +++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 Graphs/ConnectedComponents.js

diff --git a/Graphs/ConnectedComponents.js b/Graphs/ConnectedComponents.js
new file mode 100644
index 0000000000..2333a545c1
--- /dev/null
+++ b/Graphs/ConnectedComponents.js
@@ -0,0 +1,56 @@
+class GraphUnweightedUndirected {
+  // 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
+  }
+}
+
+function main () {
+  const graph = new GraphUnweightedUndirected()
+  graph.addEdge(1, 2) // Component 1
+  graph.addEdge(3, 4) // Component 2
+  graph.addEdge(3, 5) // Component 2
+  console.log(graph.connectedComponents())
+}
+
+main()