adding Kahn's Topological sorting

Author: ntedgi

README.md

@@ -33,6 +33,7 @@ Common algorithms implemented in JavaScript with [Mocha](https://mochajs.org/)/[
 
 * [Breadth First Search](https://github.com/sumtype/common-algorithms-js/blob/master/algorithms/es/breadthFirstSearch.js)
 * [Depth First Search](https://github.com/sumtype/common-algorithms-js/blob/master/algorithms/es/depthFirstSearch.js)
+* [Kahn's Topological sorting](https://github.com/sumtype/common-algorithms-js/blob/master/algorithms/es/kahnTopologicalSort.js)
 
 ### Math
 

algorithms/es/kahnTopologicalSort.js

@@ -0,0 +1,47 @@
+'use strict'
+
+const kahnTopologicalSort = edges => {
+  if (!Array.isArray(edges) || edges.length === 0) return null
+  let nodes = {}
+  let sorted = []
+  let visited = {}
+
+  let Node = function (id) {
+    this.id = id
+    this.afters = []
+  }
+
+  edges.forEach(v => {
+    let from = v[0]
+    let to = v[1]
+    if (!nodes[from]) nodes[from] = new Node(from)
+    if (!nodes[to]) nodes[to] = new Node(to)
+    nodes[from].afters.push(to)
+  })
+
+  const visit = (idstr, ancestors) => {
+    let node = nodes[idstr]
+    let id = node.id
+    if (visited[idstr]) return
+    if (!Array.isArray(ancestors)) ancestors = []
+    ancestors.push(id)
+    visited[idstr] = true
+    node.afters.forEach(afterID => {
+      if (ancestors.indexOf(afterID) >= 0) {
+        throw new Error('closed chain : ' + afterID + ' is in ' + id)
+      }
+      visit(
+        afterID.toString(),
+        ancestors.map(v => {
+          return v
+        })
+      )
+    })
+    sorted.unshift(id)
+  }
+
+  Object.keys(nodes).forEach(visit)
+
+  return sorted
+}
+export default kahnTopologicalSort

algorithms/es5/kahnTopologicalSort.js

@@ -0,0 +1,61 @@
+(function (global, factory) {
+  if (typeof define === 'function' && define.amd) {
+    define(['exports'], factory)
+  } else if (typeof exports !== 'undefined') {
+    factory(exports)
+  } else {
+    var mod = {
+      exports: {}
+    }
+    factory(mod.exports)
+    global.kahnTopologicalSort = mod.exports
+  }
+})(this, function (exports) {
+  'use strict'
+
+  Object.defineProperty(exports, '__esModule', {
+    value: true
+  })
+  var kahnTopologicalSort = function kahnTopologicalSort (edges) {
+    if (!Array.isArray(edges) || edges.length === 0) return null
+    var nodes = {}
+    var sorted = []
+    var visited = {}
+
+    var Node = function Node (id) {
+      this.id = id
+      this.afters = []
+    }
+
+    edges.forEach(function (v) {
+      var from = v[0]
+      var to = v[1]
+      if (!nodes[from]) nodes[from] = new Node(from)
+      if (!nodes[to]) nodes[to] = new Node(to)
+      nodes[from].afters.push(to)
+    })
+
+    var visit = function visit (idstr, ancestors) {
+      var node = nodes[idstr]
+      var id = node.id
+      if (visited[idstr]) return
+      if (!Array.isArray(ancestors)) ancestors = []
+      ancestors.push(id)
+      visited[idstr] = true
+      node.afters.forEach(function (afterID) {
+        if (ancestors.indexOf(afterID) >= 0) {
+          throw new Error('closed chain : ' + afterID + ' is in ' + id)
+        }
+        visit(afterID.toString(), ancestors.map(function (v) {
+          return v
+        }))
+      })
+      sorted.unshift(id)
+    }
+
+    Object.keys(nodes).forEach(visit)
+
+    return sorted
+  }
+  exports.default = kahnTopologicalSort
+})

es.js

@@ -30,7 +30,7 @@ import rayCasting from './algorithms/es/rayCasting'
 // Graph Algorithms
 import breadthFirstSearch from './algorithms/es/breadthFirstSearch'
 import depthFirstSearch from './algorithms/es/depthFirstSearch'
-
+import kahnTopologicalSort from './algorithms/es/kahnTopologicalSort'
 // Math Algorithms
 import fibonacciNumber from './algorithms/es/fibonacciNumber'
 import isPrime from './algorithms/es/isPrime'
@@ -59,7 +59,7 @@ import sorensenDiceCoefficient from './algorithms/es/sorensenDiceCoefficient'
 // Algorithm Categories
 const array = { binarySearch, bubbleSort, bucketSort, cocktailSort, countingSort, durstenfeldShuffle, gnomeSort, insertionSort, linearSearch, mergeSort, quickSort, radixSort, reservoirSampling, sattoloCycle, selectionSort, shellSort, sleepSort }
 const geometry = { bezierCurve, rayCasting }
-const graph = { breadthFirstSearch, depthFirstSearch }
+const graph = { breadthFirstSearch, depthFirstSearch, kahnTopologicalSort }
 const math = { fibonacciNumber, isPrime, powerSet, primeFactors, sieveOfAtkin, sieveOfEratosthenes }
 const string = { areAnagrams, arePalindromes, boyerMooreStringMatch, boyerMooreHorspoolStringMatch, bruteForceStringMatch, damerauLevenshteinDistance, hammingDistance, hasDuplicateCharacters, knuthMorrisPrattStringMatch, levenshteinDistance, longestCommonSubsequence, longestCommonSubstring, matchingDelimiters, rabinKarpStringMatch, sorensenDiceCoefficient }
 
@@ -68,7 +68,7 @@ export default { array, geometry, graph, math, string }
 export {
   array, binarySearch, bubbleSort, bucketSort, cocktailSort, countingSort, durstenfeldShuffle, gnomeSort, insertionSort, linearSearch, mergeSort, quickSort, radixSort, reservoirSampling, sattoloCycle, selectionSort, shellSort, sleepSort,
   geometry, bezierCurve, rayCasting,
-  graph, breadthFirstSearch, depthFirstSearch,
+  graph, breadthFirstSearch, depthFirstSearch, kahnTopologicalSort,
   math, fibonacciNumber, isPrime, powerSet, primeFactors, sieveOfAtkin, sieveOfEratosthenes,
   string, areAnagrams, arePalindromes, boyerMooreStringMatch, boyerMooreHorspoolStringMatch, bruteForceStringMatch, damerauLevenshteinDistance, hammingDistance, hasDuplicateCharacters, knuthMorrisPrattStringMatch, levenshteinDistance, longestCommonSubsequence, longestCommonSubstring, matchingDelimiters, rabinKarpStringMatch, sorensenDiceCoefficient
 }