feat: implement undirected graph data structure class

Author: francislagares

src/graph/Graph.ts

@@ -0,0 +1,60 @@
+export default interface Graph<T> {
+  numberOfNodes: number;
+  adjacentList: object;
+  addVertex(node: string): boolean;
+  addEdge(vertex: string, node: string): boolean;
+  hasEdge(vertex: string, node: string): boolean;
+  displayConnections(): void;
+}
+
+export default class Graph<T> implements Graph<T> {
+  public constructor() {
+    this.numberOfNodes = 0;
+    this.adjacentList = {};
+  }
+
+  public addVertex(node: string): boolean {
+    // Check if vertex already exists on adjacentList
+    if (!this.adjacentList[node]) {
+      this.adjacentList[node] = [];
+    } else {
+      throw new Error('The node already exists');
+    }
+    this.numberOfNodes++;
+    return true;
+  }
+
+  public addEdge(vertex: string, node: string): boolean {
+    // If vertex1 exists in adjacentList add vertex2 to the adjacents
+    // If vertex2 exists in adjacentList add vertex1 to the adjacents
+    let hasEdge = this.hasEdge(vertex, node);
+    if (!hasEdge) {
+      this.adjacentList[vertex].push(node);
+      this.adjacentList[node].push(vertex);
+    } else {
+      throw new Error('The node does not exist');
+    }
+    return true;
+  }
+
+  public hasEdge(vertex: string, node: string): boolean {
+    let adjacents = this.adjacentList[vertex];
+    for (let i = 0; i < adjacents.length; i++) {
+      if (node === adjacents[i]) return true;
+    }
+    return false;
+  }
+
+  public displayConnections(): void {
+    const allNodes = Object.keys(this.adjacentList);
+    for (let node of allNodes) {
+      let nodeConnections = this.adjacentList[node];
+      let connections = '';
+      let vertex: string;
+      for (vertex of nodeConnections) {
+        connections += vertex + ' ';
+      }
+      console.log(node + ' --> ' + connections);
+    }
+  }
+}

src/graph/__tests__/Graph.test.ts

@@ -0,0 +1,71 @@
+import Graph from '../Graph';
+
+describe('Graphs', () => {
+  test('create an empty graph', () => {
+    const graph = new Graph();
+
+    expect(graph).toBeDefined();
+  });
+
+  test('add a new vertex to the graph', () => {
+    const graph = new Graph();
+
+    graph.addVertex('0');
+    graph.addVertex('1');
+    graph.addVertex('2');
+    graph.addVertex('3');
+    graph.addVertex('4');
+    graph.addVertex('5');
+    graph.addVertex('6');
+
+    expect(graph.numberOfNodes).toBe(7);
+    expect(graph.adjacentList[0]).toEqual([]);
+    expect(graph.adjacentList[1]).toEqual([]);
+    expect(graph.adjacentList[2]).toEqual([]);
+    expect(graph.adjacentList[3]).toEqual([]);
+    expect(graph.adjacentList[4]).toEqual([]);
+    expect(graph.adjacentList[5]).toEqual([]);
+    expect(graph.adjacentList[6]).toEqual([]);
+  });
+
+  test('throws error if vertex already exists', () => {
+    try {
+      const graph = new Graph();
+
+      graph.addVertex('0');
+      graph.addVertex('1');
+      graph.addVertex('2');
+
+      expect(graph.addVertex('2')).toThrowError();
+    } catch (error) {
+      expect(error).toBeInstanceOf(Error);
+      expect(error).toHaveProperty('message', 'The node already exists');
+    }
+  });
+
+  test('add edges to graph', () => {
+    const graph = new Graph();
+
+    graph.addVertex('0');
+    graph.addVertex('1');
+    graph.addVertex('2');
+    graph.addVertex('3');
+    graph.addVertex('4');
+    graph.addVertex('5');
+    graph.addVertex('6');
+
+    graph.addEdge('3', '1');
+    graph.addEdge('3', '4');
+    graph.addEdge('4', '2');
+    graph.addEdge('4', '5');
+    graph.addEdge('1', '2');
+    graph.addEdge('1', '0');
+    graph.addEdge('0', '2');
+    graph.addEdge('6', '5');
+
+    expect(graph.hasEdge('3', '4')).toBeTruthy();
+    expect(graph.hasEdge('3', '1')).toBeTruthy();
+    expect(graph.hasEdge('4', '5')).toBeTruthy();
+    expect(graph.hasEdge('1', '2')).toBeTruthy();
+  });
+});

src/index.ts

@@ -6,3 +6,4 @@ import './doubly-linked-list/DoublyLinkedList';
 import './stack/StackClass';
 import './queue/QueueClass';
 import './tree/binary-search/BinarySearchTree';
+import './graph/Graph';