4.1 Routes between nodes - my solution

Author: amejiarosario

src/trees-and-graphs/graph.js

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+const Queue = require('../stacks-and-queues/queue');
+/**
+ * Digraph
+ */
+class Graph {
+  constructor() {
+    this.nodes = [];
+  }
+
+  /**
+   * use adjacency list to store nodes and more
+   *
+   * O(1)
+   *
+   * @param a
+   * @param b
+   */
+  add(a, b) {
+    if(!this.nodes[a]) {
+      this.nodes[a] = [];
+    }
+
+    this.nodes[a].push(b);
+  }
+
+  /**
+   * Depth-first search
+   * @param node
+   */
+  dfs(node) {
+
+  }
+}
+
+/**
+ * Breadth-first search
+ * @param node
+ */
+Graph.prototype.bfs = function* (node) {
+  const queue = new Queue();
+
+  queue.add(node);
+
+  while(!queue.isEmpty()){
+    const adjacents = this.nodes[queue.remove()];
+    yield adjacents;
+    adjacents.forEach(function (adjNode) {
+      queue.add(adjNode);
+    });
+  }
+};
+
+module.exports = Graph;

src/trees-and-graphs/graph.spec.js

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+const expect = require('chai').expect;
+const Graph = require('./graph');
+
+describe('Graph', function () {
+  let graph;
+
+  beforeEach(function () {
+    graph = new Graph();
+  });
+
+  describe('add', function () {
+    it('should add two elements', function () {
+      graph.add(0, 1);
+      expect(graph.nodes[0]).to.eql([1]);
+    });
+
+    it('should allow one element to have two children', function () {
+      graph.add(0, 1);
+      graph.add(0, 2);
+      expect(graph.nodes[0]).to.eql([1, 2]);
+    });
+
+    it('should store complex data', function () {
+      let a = {a:1};
+      let b = {b:2};
+
+      graph.add(a, b);
+      expect(graph.nodes[a]).to.eql([b]);
+    });
+  });
+
+  describe('bfs', function () {
+    beforeEach(function () {
+      graph.add(0, 1);
+      graph.add(0, 2);
+      graph.add(1, 3);
+    });
+
+    it('should get all adjancent in the first level', function () {
+      const bfs = graph.bfs(0);
+      expect(bfs.next().value).to.eql([1, 2]);
+    });
+
+    it('should get 2nd level adjacents', function () {
+      const bfs = graph.bfs(0);
+      bfs.next();
+      expect(bfs.next().value).to.eql([3]);
+      expect(bfs.next().value).to.equal(undefined);
+    });
+  });
+});

src/trees-and-graphs/routes-between-nodes.js

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+const Graph = require('./graph');
+const Queue = require('../stacks-and-queues/queue');
+
+/**
+ * Test if two nodes are connected using BFS
+ * @param node1
+ * @param node2
+ * @returns {boolean}
+ */
+Graph.prototype.isConnected = function(node1, node2) {
+  const queue = new Queue();
+
+  queue.add(node1);
+
+  while(!queue.isEmpty()) {
+    const current = queue.remove();
+
+    if(current === node2) {
+      return true;
+    }
+
+    (this.nodes[current] || []).forEach(function (node) {
+      queue.add(node);
+    });
+  }
+
+  return false;
+};
+
+module.exports = Graph;

src/trees-and-graphs/routes-between-nodes.spec.js

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+const expect = require('chai').expect;
+const Graph = require('./routes-between-nodes');
+
+describe('Graph: is connected', function () {
+  let graph;
+
+  beforeEach(function () {
+    graph = new Graph();
+  });
+
+  describe('.isConnected', function () {
+    it('should return true if connected', function () {
+      graph.add(0, 1);
+      graph.add(1, 2);
+      expect(graph.isConnected(0, 2)).to.equal(true);
+    });
+
+    it('should return false if connected', function () {
+      graph.add(0, 1);
+      graph.add(2, 3);
+      expect(graph.isConnected(0, 3)).to.equal(false);
+    });
+  });
+});