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Commitc1a1b2f

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feat(graphs): add Tarjan's algorithm for SCC
Fixmgechev#98
1 parent1c292fe commitc1a1b2f

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4 files changed

+111
-2
lines changed

4 files changed

+111
-2
lines changed

‎package.json

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@@ -16,7 +16,7 @@
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"jshint-stylish":"^1.0.0"
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},
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"scripts": {
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"test":"echo\"Error: notest specified\" && exit 1"
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"test":"gulptest"
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},
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"repository": {
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"type":"git",
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(function(exports){
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/**
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* Tarjan's algorithm for finding the connected components in a graph.<br><br>
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* Time complexity: O(|E| + |V|) where E is a number of edges and |V|
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* is the number of nodes.
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*
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*@public
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*@module graphs/others/tarjan-connected-components
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*@param {Array} graph Adjacency list, which represents the graph.
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*@returns {Array} Connected components.
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*
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*@example
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* var tarjanConnectedComponents =
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* require('path-to-algorithms/src/graphs/' +
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* 'others/tarjan-connected-components').tarjanConnectedComponents;
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* var graph = {
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* v1: ['v2', 'v5'],
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* v2: [],
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* v3: ['v1', 'v2', 'v4', 'v5'],
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* v4: [],
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* v5: []
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* };
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* var vertices = topsort(graph); // ['v3', 'v4', 'v1', 'v5', 'v2']
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*/
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functiontarjanConnectedComponents(graph){
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graph=graph||{};
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constindexes={};
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constlowIndexes={};
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constonStack={};
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constresult=[];
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conststack=[];
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letindex=1;
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constconnectedComponent=node=>{
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stack.push(node);
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onStack[node]=true;
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indexes[node]=index;
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lowIndexes[node]=index;
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index+=1;
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graph[node].forEach(n=>{
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if(indexes[n]===undefined){
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connectedComponent(n);
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lowIndexes[node]=Math.min(lowIndexes[n],lowIndexes[node]);
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}elseif(onStack[n]){
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lowIndexes[node]=Math.min(lowIndexes[node],indexes[n]);
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}
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});
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// This is a "root" node
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constcc=[];
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if(indexes[node]===lowIndexes[node]){
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letcurrent;
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do{
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current=stack.pop();
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onStack[current]=false;
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cc.push(current);
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}while(stack.length>0&&node!==current);
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result.push(cc);
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}
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};
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Object.keys(graph)
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.forEach(n=>!indexes[n]&&connectedComponent(n));
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returnresult;
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}
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exports.tarjanConnectedComponents=tarjanConnectedComponents;
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}(typeofexports==='undefined' ?window :exports));

‎src/graphs/others/topological-sort.js

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/**
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* Topological sort algorithm of a directed acyclic graph.<br><br>
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* Time complexity: O(|E|) where E is a number of edges.
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* Time complexity: O(|E| + |V|) where E is a number of edges
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* and |V| is the number of nodes.
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*
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*@public
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*@module graphs/others/topological-sort
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vartj=require('../../../src/graphs/others/tarjan-connected-components').tarjanConnectedComponents;
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varnonConnected={
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v1:[],
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v2:[],
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v3:[],
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v4:[],
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v5:[]
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};
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varcyclicGraph={
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v1:['v2'],
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v2:['v3'],
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v3:['v4'],
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v4:['v5'],
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v5:['v1']
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};
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describe('Tarjan\'s algorithm for finding connected components',function(){
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'use strict';
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it('should be defined',function(){
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expect(typeoftj).toBe('function');
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});
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it('should return an array',function(){
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expect(tj()instanceofArray).toBeTruthy();
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});
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it('should work with non-connected graphs',function(){
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expect(tj(nonConnected)).toEqual([['v1'],['v2'],['v3'],['v4'],['v5']]);
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});
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it('should workw ith cycles',()=>{
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expect(tj(cyclicGraph)).toEqual([['v5','v4','v3','v2','v1']]);
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});
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});

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