Implemented method to generate adjacency list for graph

src/data-structures/graph/Graph.js

@@ -188,6 +188,36 @@ export default class Graph {
     return adjacencyMatrix;
   }
 
+  /**
+   * @returns {*[{}]}
+   */
+  getAdjacencyList() {
+    const edges = this.getAllEdges();
+    const adjacencyList = {};
+
+    edges.forEach((edge) => {
+      const { weight } = edge;
+      const startVertexValue = edge.startVertex.value;
+      const endVertexValue = edge.endVertex.value;
+
+      if (adjacencyList[startVertexValue]) {
+        adjacencyList[edge.startVertex.value].push({ weight, value: endVertexValue });
+      } else {
+        adjacencyList[startVertexValue] = [{ weight, value: endVertexValue }];
+      }
+
+      if (!this.isDirected) {
+        if (adjacencyList[endVertexValue]) {
+          adjacencyList[endVertexValue].push({ weight, value: startVertexValue });
+        } else {
+          adjacencyList[endVertexValue] = [{ weight, value: startVertexValue }];
+        }
+      }
+    });
+
+    return adjacencyList;
+  }
+
   /**
    * @return {string}
    */

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

@@ -385,4 +385,59 @@ describe('Graph', () => {
       [Infinity, Infinity, Infinity, Infinity],
     ]);
   });
+
+  it('should generate adjacency list 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, 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();
+    graph
+      .addEdge(edgeAB)
+      .addEdge(edgeBC)
+      .addEdge(edgeCD)
+      .addEdge(edgeBD);
+
+    const adjacencyList = graph.getAdjacencyList();
+
+    expect(adjacencyList).toEqual({
+      A: [{ value: 'B', weight: 2 }],
+      B: [{ value: 'A', weight: 2 }, { value: 'C', weight: 1 }, { value: 'D', weight: 7 }],
+      C: [{ value: 'B', weight: 1 }, { value: 'D', weight: 5 }],
+      D: [{ value: 'C', weight: 5 }, { value: 'B', weight: 7 }],
+    });
+  });
+
+  it('should generate adjacency list 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 adjacencyList = graph.getAdjacencyList();
+
+    expect(adjacencyList).toEqual({
+      A: [{ value: 'B', weight: 2 }],
+      B: [{ value: 'C', weight: 1 }, { value: 'D', weight: 7 }],
+      C: [{ value: 'D', weight: 5 }],
+    });
+  });
 });