Bellman Ford added

src/main/java/com/packt/datastructuresandalg/lesson6/graph/BellmanFord.java

@@ -0,0 +1,81 @@
+import java.util.Arrays;
+
+public class BellmanFord {
+ class Edge {
+ int source, destination, weight;
+
+ Edge(int source, int destination, int weight) {
+ this.source = source;
+ this.destination = destination;
+ this.weight = weight;
+ }
+ }
+
+ int vertices, edges;
+ Edge[] edgeList;
+
+ BellmanFord(int vertices, int edges) {
+ this.vertices = vertices;
+ this.edges = edges;
+ edgeList = new Edge[edges];
+ }
+
+ void addEdge(int index, int source, int destination, int weight) {
+ edgeList[index] = new Edge(source, destination, weight);
+ }
+
+ void bellmanFord(int source) {
+ int[] distance = new int[vertices];
+ Arrays.fill(distance, Integer.MAX_VALUE);
+ distance[source] = 0;
+
+ // Relax all edges |V| - 1 times.
+ for (int i = 1; i < vertices; ++i) {
+ for (int j = 0; j < edges; ++j) {
+ int u = edgeList[j].source;
+ int v = edgeList[j].destination;
+ int weight = edgeList[j].weight;
+ if (distance[u] != Integer.MAX_VALUE && distance[u] + weight < distance[v]) {
+ distance[v] = distance[u] + weight;
+ }
+ }
+ }
+
+ // Check for negative-weight cycles.
+ for (int j = 0; j < edges; ++j) {
+ int u = edgeList[j].source;
+ int v = edgeList[j].destination;
+ int weight = edgeList[j].weight;
+ if (distance[u] != Integer.MAX_VALUE && distance[u] + weight < distance[v]) {
+ System.out.println("Graph contains negative weight cycle");
+ return;
+ }
+ }
+
+ printSolution(distance, source);
+ }
+
+ void printSolution(int[] distance, int source) {
+ System.out.println("Vertex Distance from Source " + source);
+ for (int i = 0; i < vertices; ++i)
+ System.out.println(i + "\t\t" + distance[i]);
+ }
+
+ public static void main(String[] args) {
+ int vertices = 5;
+ int edges = 8;
+
+ BellmanFord graph = new BellmanFord(vertices, edges);
+
+ graph.addEdge(0, 0, 1, -1);
+ graph.addEdge(1, 0, 2, 4);
+ graph.addEdge(2, 1, 2, 3);
+ graph.addEdge(3, 1, 3, 2);
+ graph.addEdge(4, 1, 4, 2);
+ graph.addEdge(5, 3, 2, 5);
+ graph.addEdge(6, 3, 1, 1);
+ graph.addEdge(7, 4, 3, -3);
+
+ graph.bellmanFord(0);
+ }
+}