feat(graph) add/remove vertex

Author: amejiarosario

lib/data-structures/graphs/graph.js

@@ -2,13 +2,42 @@ const Node = require('./node');
 
 /**
  * Graph that uses an adjacent list
+ *
+ * Most common operations:
+ * - Add vertex
+ * - Add edge
+ * - Remove vertex
+ * - Remove edge
+ * - Query (query if two vertices are connected)
+ *
+ *  - Graph search (BFS, DFS)
+ *
+ * - Find path (between two vertices)
+ * - Find all paths (between two vertices)
+ * - Find shortest paths (between two vertices)
  */
 class Graph {
-  constructor() {
+  constructor(edgeDirection = Graph.DIRECTED) {
     this.nodes = new Map();
+    this.edgeDirection = edgeDirection;
   }
 
-  addVertex() {
+  addVertex(value) {
+    if(this.nodes.has(value)) {
+      return this.nodes.get(value);
+    } else {
+      const vertex = new Node(value);
+      this.nodes.set(value, vertex);
+      return vertex;
+    }
+  }
 
+  removeVertex(value) {
+    return this.nodes.delete(value);
   }
-}
+}
+
+Graph.UNDIRECTED = Symbol('directed graph'); // one-way edges
+Graph.DIRECTED = Symbol('undirected graph'); // two-ways edges
+
+module.exports = Graph;

lib/data-structures/graphs/graph.spec.js

@@ -7,9 +7,30 @@ describe('Graph', () => {
     graph = new Graph();
   });
 
-  xdescribe('#addVertex', () => {
+  describe('#addVertex', () => {
     it('should add vertex to graph', () => {
-      graph.addVertex()
+      const node = graph.addVertex('a');
+      expect(node.value).toBe('a');
+      expect(graph.nodes.size).toBe(1);
+    });
+
+    it('should not add duplicated values', () => {
+      const node1 = graph.addVertex('a');
+      const node2 = graph.addVertex('a');
+      expect(graph.nodes.size).toBe(1);
+      expect(node1).toBe(node2);
+    });
+  });
+
+  describe('#removeVertex', () => {
+    beforeEach(() => {
+      graph.addVertex('a');
+    });
+
+    it('should remove vertex', () => {
+      expect(graph.removeVertex('a')).toBe(true);
+      expect(graph.nodes.size).toBe(0);
+      expect(graph.removeVertex('a')).toBe(false);
     });
   });
 });