Added bellmanFord function

apsp.js

@@ -0,0 +1,47 @@
+/**
+ * @param {Graph} graph
+ * @param {GraphVertex} startVertex
+ * @return {{distances, previousVertices}}
+ */
+
+
+export default function bellmanFord(graph, startVertex) {
+  const distances = {};
+  const previousVertices = {};
+
+
+  distances[startVertex.getKey()] = 0;  //starting node
+
+  graph.getAllVertices().forEach((vertex) => {
+    previousVertices[vertex.getKey()] = null;
+    if (vertex.getKey() !== startVertex.getKey()) {
+      distances[vertex.getKey()] = Infinity;  //init all dists with infinity
+    }
+  });
+
+  // We need (|V| - 1) iterations.
+  for (let iteration = 0; iteration < (graph.getAllVertices().length - 1); iteration += 1) {
+
+    Object.keys(distances).forEach((vertexKey) => {
+      const vertex = graph.getVertexByKey(vertexKey);
+
+      // Go through all vertex edges.
+      graph.getNeighbors(vertex).forEach((neighbor) => {
+        const edge = graph.findEdge(vertex, neighbor);
+        // Find out if the distance to the neighbor is shorter in this iteration
+        // then in previous one.
+        const distanceToVertex = distances[vertex.getKey()];
+        const distanceToNeighbor = distanceToVertex + edge.weight;
+        if (distanceToNeighbor < distances[neighbor.getKey()]) {
+          distances[neighbor.getKey()] = distanceToNeighbor;
+          previousVertices[neighbor.getKey()] = vertex;
+        }
+      });
+    });
+  }
+
+  return {
+    distances,
+    previousVertices,
+  };
+}