Add Bellman-Ford.

Author: trekhleb

src/algorithms/graph/bellman-ford/__test__/bellmanFord.test.js

@@ -4,7 +4,68 @@ import Graph from '../../../../data-structures/graph/Graph';
 import bellmanFord from '../bellmanFord';
 
 describe('bellmanFord', () => {
-  it('should find minimum paths to all vertices', () => {
+  it('should find minimum paths to all vertices for undirected graph', () => {
+    const vertexA = new GraphVertex('A');
+    const vertexB = new GraphVertex('B');
+    const vertexC = new GraphVertex('C');
+    const vertexD = new GraphVertex('D');
+    const vertexE = new GraphVertex('E');
+    const vertexF = new GraphVertex('F');
+    const vertexG = new GraphVertex('G');
+    const vertexH = new GraphVertex('H');
+
+    const edgeAB = new GraphEdge(vertexA, vertexB, 4);
+    const edgeAE = new GraphEdge(vertexA, vertexE, 7);
+    const edgeAC = new GraphEdge(vertexA, vertexC, 3);
+    const edgeBC = new GraphEdge(vertexB, vertexC, 6);
+    const edgeBD = new GraphEdge(vertexB, vertexD, 5);
+    const edgeEC = new GraphEdge(vertexE, vertexC, 8);
+    const edgeED = new GraphEdge(vertexE, vertexD, 2);
+    const edgeDC = new GraphEdge(vertexD, vertexC, 11);
+    const edgeDG = new GraphEdge(vertexD, vertexG, 10);
+    const edgeDF = new GraphEdge(vertexD, vertexF, 2);
+    const edgeFG = new GraphEdge(vertexF, vertexG, 3);
+    const edgeEG = new GraphEdge(vertexE, vertexG, 5);
+
+    const graph = new Graph();
+    graph
+      .addVertex(vertexH)
+      .addEdge(edgeAB)
+      .addEdge(edgeAE)
+      .addEdge(edgeAC)
+      .addEdge(edgeBC)
+      .addEdge(edgeBD)
+      .addEdge(edgeEC)
+      .addEdge(edgeED)
+      .addEdge(edgeDC)
+      .addEdge(edgeDG)
+      .addEdge(edgeDF)
+      .addEdge(edgeFG)
+      .addEdge(edgeEG);
+
+    const { distances, previousVertices } = bellmanFord(graph, vertexA);
+
+    expect(distances).toEqual({
+      H: Infinity,
+      A: 0,
+      B: 4,
+      E: 7,
+      C: 3,
+      D: 9,
+      G: 12,
+      F: 11,
+    });
+
+    expect(previousVertices.F.getKey()).toBe('D');
+    expect(previousVertices.D.getKey()).toBe('B');
+    expect(previousVertices.B.getKey()).toBe('A');
+    expect(previousVertices.G.getKey()).toBe('E');
+    expect(previousVertices.C.getKey()).toBe('A');
+    expect(previousVertices.A).toBeNull();
+    expect(previousVertices.H).toBeNull();
+  });
+
+  it('should find minimum paths to all vertices for directed graph with negative edge weights', () => {
     const vertexS = new GraphVertex('S');
     const vertexE = new GraphVertex('E');
     const vertexA = new GraphVertex('A');

src/algorithms/graph/dijkstra/__test__/dijkstra.test.js

@@ -4,7 +4,7 @@ import Graph from '../../../../data-structures/graph/Graph';
 import dijkstra from '../dijkstra';
 
 describe('dijkstra', () => {
-  it('should find minimum paths to all vertices', () => {
+  it('should find minimum paths to all vertices for undirected graph', () => {
     const vertexA = new GraphVertex('A');
     const vertexB = new GraphVertex('B');
     const vertexC = new GraphVertex('C');
@@ -64,4 +64,54 @@ describe('dijkstra', () => {
     expect(previousVertices.A).toBeNull();
     expect(previousVertices.H).toBeNull();
   });
+
+  it('should find minimum paths to all vertices for directed graph with negative edge weights', () => {
+    const vertexS = new GraphVertex('S');
+    const vertexE = new GraphVertex('E');
+    const vertexA = new GraphVertex('A');
+    const vertexD = new GraphVertex('D');
+    const vertexB = new GraphVertex('B');
+    const vertexC = new GraphVertex('C');
+    const vertexH = new GraphVertex('H');
+
+    const edgeSE = new GraphEdge(vertexS, vertexE, 8);
+    const edgeSA = new GraphEdge(vertexS, vertexA, 10);
+    const edgeED = new GraphEdge(vertexE, vertexD, 1);
+    const edgeDA = new GraphEdge(vertexD, vertexA, -4);
+    const edgeDC = new GraphEdge(vertexD, vertexC, -1);
+    const edgeAC = new GraphEdge(vertexA, vertexC, 2);
+    const edgeCB = new GraphEdge(vertexC, vertexB, -2);
+    const edgeBA = new GraphEdge(vertexB, vertexA, 1);
+
+    const graph = new Graph(true);
+    graph
+      .addVertex(vertexH)
+      .addEdge(edgeSE)
+      .addEdge(edgeSA)
+      .addEdge(edgeED)
+      .addEdge(edgeDA)
+      .addEdge(edgeDC)
+      .addEdge(edgeAC)
+      .addEdge(edgeCB)
+      .addEdge(edgeBA);
+
+    const { distances, previousVertices } = dijkstra(graph, vertexS);
+
+    expect(distances).toEqual({
+      H: Infinity,
+      S: 0,
+      A: 5,
+      B: 5,
+      C: 7,
+      D: 9,
+      E: 8,
+    });
+
+    expect(previousVertices.H).toBeNull();
+    expect(previousVertices.S).toBeNull();
+    expect(previousVertices.B.getKey()).toBe('C');
+    expect(previousVertices.C.getKey()).toBe('A');
+    expect(previousVertices.A.getKey()).toBe('D');
+    expect(previousVertices.D.getKey()).toBe('E');
+  });
 });