Add Prim.

src/data-structures/graph/Graph.js

@@ -110,12 +110,18 @@ export default class Graph {
     return null;
   }
 
+  /**
+   * @return {number}
+   */
   getWeight() {
     return this.getAllEdges().reduce((weight, graphEdge) => {
       return weight + graphEdge.weight;
     }, 0);
   }
 
+  /**
+   * @return {string}
+   */
   toString() {
     return Object.keys(this.vertices).toString();
   }

src/data-structures/graph/GraphEdge.js

@@ -19,4 +19,11 @@ export default class GraphEdge {
 
     return `${startVertexKey}_${endVertexKey}`;
   }
+
+  /**
+   * @return {string}
+   */
+  toString() {
+    return this.getKey();
+  }
 }

src/data-structures/graph/GraphVertex.js

@@ -1,6 +1,9 @@
 import LinkedList from '../linked-list/LinkedList';
 
 export default class GraphVertex {
+  /**
+   * @param {*} value
+   */
   constructor(value) {
     if (value === undefined) {
       throw new Error('Graph vertex must have a value');
@@ -37,6 +40,13 @@ export default class GraphVertex {
     return edges.map(neighborsConverter);
   }
 
+  /**
+   * @return {GraphEdge[]}
+   */
+  getEdges() {
+    return this.edges.toArray().map(linkedListNode => linkedListNode.value);
+  }
+
   /**
    * @param {GraphEdge} requiredEdge
    * @returns {boolean}

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

@@ -8,6 +8,7 @@ describe('GraphEdge', () => {
     const edge = new GraphEdge(startVertex, endVertex);
 
     expect(edge.getKey()).toBe('A_B');
+    expect(edge.toString()).toBe('A_B');
     expect(edge.startVertex).toEqual(startVertex);
     expect(edge.endVertex).toEqual(endVertex);
     expect(edge.weight).toEqual(0);

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

@@ -21,17 +21,20 @@ describe('GraphVertex', () => {
     expect(vertex.toString()).toBe('A');
     expect(vertex.getKey()).toBe('A');
     expect(vertex.edges.toString()).toBe('');
+    expect(vertex.getEdges()).toEqual([]);
   });
 
   it('should add edges to vertex and check if it exists', () => {
     const vertexA = new GraphVertex('A');
-    const vertexB = new GraphVertex('A');
+    const vertexB = new GraphVertex('B');
 
     const edgeAB = new GraphEdge(vertexA, vertexB);
     vertexA.addEdge(edgeAB);
 
     expect(vertexA.hasEdge(edgeAB)).toBeTruthy();
     expect(vertexB.hasEdge(edgeAB)).toBeFalsy();
+    expect(vertexA.getEdges().length).toBe(1);
+    expect(vertexA.getEdges()[0].toString()).toBe('A_B');
   });
 
   it('should return vertex neighbors in case if current node is start one', () => {