Updated kahn's algorithm

Author: root

Graphs/KahnsAlgorithm.js

@@ -0,0 +1,45 @@
+import Queue from '../Data-Structures/Queue/Queue'
+
+/**
+ * @author {RaviSadam}
+ * @name KahnsAlgorithm
+ * @description -
+ * Kahn's Algorithm implementation in JavaScript
+ * @summary
+ * Kahn's Algorithm is used for finding the topological sorting order of directed acyclic graph
+ *
+ * @param graph - Graph (adjacency list)
+ * @param n - Size of graph
+ * @returns {Array} - null if cycle is detected or else result array
+ *
+ */
+
+export function KahnsAlgorithm(graph, n) {
+  if (n === null || n === undefined) throw Error('Invalid n was given')
+  const inDegree = Array(n).fill(0)
+  const result = []
+  for (const neigbhours of graph) {
+    for (const neigbhour of neigbhours) {
+      inDegree[neigbhour] += 1
+    }
+  }
+  const queue = new Queue()
+
+  for (let i = 0; i < n; i++) {
+    if (inDegree[i] === 0) {
+      queue.enqueue(i)
+    }
+  }
+  while (queue.length !== 0) {
+    const node = queue.dequeue()
+    result.push(node)
+    for (const neigbhour of graph[node]) {
+      inDegree[neigbhour] -= 1
+      if (inDegree[neigbhour] == 0) {
+        queue.enqueue(neigbhour)
+      }
+    }
+  }
+  if (result.length !== n) return null
+  return result
+}

Graphs/test/KahnsAlgorithm.test.js

@@ -0,0 +1,13 @@
+import { KahnsAlgorithm } from '../KahnsAlgorithm'
+
+test('Graph without cycle', () => {
+  const graph = [[], [], [3], [1], [0, 1], [0, 2]]
+
+  expect(KahnsAlgorithm(graph, 6)).toEqual([4, 5, 0, 2, 3, 1])
+})
+
+test('Graph with cycle', () => {
+  const graph = [[2], [], [3, 5], [0, 1], [0, 2]]
+
+  expect(KahnsAlgorithm(graph, 6)).toBe(null)
+})