Generate adjacency matrix for graph.

Author: trekhleb

src/data-structures/graph/Graph.js

@@ -158,6 +158,43 @@ export default class Graph {
     return this;
   }
 
+  /**
+   * @return {object}
+   */
+  getVerticesIndices() {
+    const verticesIndices = {};
+    this.getAllVertices().forEach((vertex, index) => {
+      verticesIndices[vertex.getKey()] = index;
+    });
+
+    return verticesIndices;
+  }
+
+  /**
+   * @return {*[][]}
+   */
+  getAdjacencyMatrix() {
+    const vertices = this.getAllVertices();
+    const verticesIndices = this.getVerticesIndices();
+
+    // Init matrix with zeros.
+    const adjacencyMatrix = Array(vertices.length).fill(null).map(() => {
+      return Array(vertices.length).fill(0);
+    });
+
+    // Fill the columns.
+    vertices.forEach((vertex, vertexIndex) => {
+      vertex.getNeighbors().forEach((neighbor) => {
+        const neighborIndex = verticesIndices[neighbor.getKey()];
+        adjacencyMatrix[vertexIndex][neighborIndex] = this.isDirected ?
+          this.findEdge(vertex, neighbor).weight :
+          1;
+      });
+    });
+
+    return adjacencyMatrix;
+  }
+
   /**
    * @return {string}
    */

src/data-structures/graph/__test__/Graph.test.js

@@ -300,4 +300,85 @@ describe('Graph', () => {
     expect(graph.getNeighbors(vertexD).length).toBe(1);
     expect(graph.getNeighbors(vertexD)[0].getKey()).toBe(vertexC.getKey());
   });
+
+  it('should return vertices indices', () => {
+    const vertexA = new GraphVertex('A');
+    const vertexB = new GraphVertex('B');
+    const vertexC = new GraphVertex('C');
+    const vertexD = new GraphVertex('D');
+
+    const edgeAB = new GraphEdge(vertexA, vertexB);
+    const edgeBC = new GraphEdge(vertexB, vertexC);
+    const edgeCD = new GraphEdge(vertexC, vertexD);
+    const edgeBD = new GraphEdge(vertexB, vertexD);
+
+    const graph = new Graph();
+    graph
+      .addEdge(edgeAB)
+      .addEdge(edgeBC)
+      .addEdge(edgeCD)
+      .addEdge(edgeBD);
+
+    const verticesIndices = graph.getVerticesIndices();
+    expect(verticesIndices).toEqual({
+      A: 0,
+      B: 1,
+      C: 2,
+      D: 3,
+    });
+  });
+
+  it('should generate adjacency matrix for undirected graph', () => {
+    const vertexA = new GraphVertex('A');
+    const vertexB = new GraphVertex('B');
+    const vertexC = new GraphVertex('C');
+    const vertexD = new GraphVertex('D');
+
+    const edgeAB = new GraphEdge(vertexA, vertexB);
+    const edgeBC = new GraphEdge(vertexB, vertexC);
+    const edgeCD = new GraphEdge(vertexC, vertexD);
+    const edgeBD = new GraphEdge(vertexB, vertexD);
+
+    const graph = new Graph();
+    graph
+      .addEdge(edgeAB)
+      .addEdge(edgeBC)
+      .addEdge(edgeCD)
+      .addEdge(edgeBD);
+
+    const adjacencyMatrix = graph.getAdjacencyMatrix();
+    expect(adjacencyMatrix).toEqual([
+      [0, 1, 0, 0],
+      [1, 0, 1, 1],
+      [0, 1, 0, 1],
+      [0, 1, 1, 0],
+    ]);
+  });
+
+  it('should generate adjacency matrix for directed graph', () => {
+    const vertexA = new GraphVertex('A');
+    const vertexB = new GraphVertex('B');
+    const vertexC = new GraphVertex('C');
+    const vertexD = new GraphVertex('D');
+
+    const edgeAB = new GraphEdge(vertexA, vertexB, 2);
+    const edgeBC = new GraphEdge(vertexB, vertexC, 1);
+    const edgeCD = new GraphEdge(vertexC, vertexD, 5);
+    const edgeBD = new GraphEdge(vertexB, vertexD, 7);
+
+    const graph = new Graph(true);
+    graph
+      .addEdge(edgeAB)
+      .addEdge(edgeBC)
+      .addEdge(edgeCD)
+      .addEdge(edgeBD);
+
+    const adjacencyMatrix = graph.getAdjacencyMatrix();
+    expect(adjacencyMatrix).toEqual([
+      [0, 2, 0, 0],
+      [0, 0, 1, 7],
+      [0, 0, 0, 5],
+      [0, 0, 0, 0],
+    ]);
+  });
 });