2nd Method Bellman Ford

Author: akashdeep023

36-Graphs_(Part-IV)/GraphsP4_BellmanFord.java

@@ -44,7 +44,7 @@ public static void createGraph(ArrayList<Edge>[] graph) {
         graph[4].add(new Edge(4, 1, -1));
     }
 
-    // Bellman Ford Algorithm (Shortest Path Src to All vertices) --------------------------------
+    // Bellman Ford Algorithm (Shortest Path Src to All vertices) -------------------------------- TC -> O(V*E)
     public static void bellmanFord(ArrayList<Edge>[] graph, int src) {
         // Create a Array to store distances & initialize
         int[] dist = new int[graph.length];
@@ -55,8 +55,8 @@ public static void bellmanFord(ArrayList<Edge>[] graph, int src) {
         }
         int V = graph.length;
 
-        for (int i = 0; i < V - 1; i++) { // Algorithm loop
-            for (int j = 0; j < graph.length; j++) { // Vertices loop
+        for (int i = 0; i < V - 1; i++) { // Algorithm loop - O(V)
+            for (int j = 0; j < graph.length; j++) { // Vertices loop - (E)
                 for (int k = 0; k < graph[j].size(); k++) { // Edge loop
                     Edge e = graph[j].get(k);
                     int u = e.src;
@@ -73,6 +73,60 @@ public static void bellmanFord(ArrayList<Edge>[] graph, int src) {
         }
     }
 
+    // 2nd Sorted Method with sort code (Bellman Ford) --------------------------------
+    // Create Graph ---
+    public static void createGraph2(ArrayList<Edge> graph) { // Edges graph
+        /*  
+         *              (-1)
+         *        1 ←—————————— 4 
+         *      ↗ |             ↑           Edge = 6
+         *  (2)/  |             |           Vertices = 5 (nodes)
+         *    /   |             |
+         *  0     |(-4)         |(4)
+         *    \   |             |
+         *  (4)\  |             |
+         *      ↘ ↓             |
+         *        2 ——————————→ 3
+         *              (2)
+         */
+        graph.add(new Edge(0, 1, 2));
+        graph.add(new Edge(0, 2, 4));
+
+        graph.add(new Edge(1, 2, -4));
+
+        graph.add(new Edge(2, 3, 2));
+
+        graph.add(new Edge(3, 4, 4));
+
+        graph.add(new Edge(4, 1, -1));
+    }
+
+    // Bellman Ford Algorithm (Shortest Path Src to All vertices) -------------------------------- TC -> O(V*E)
+    public static void bellmanFord2(ArrayList<Edge> graph, int src, int V) {
+        // Create a Array to store distances & initialize
+        int[] dist = new int[V];
+        for (int i = 0; i < dist.length; i++) {
+            if (i != src) {
+                dist[i] = Integer.MAX_VALUE;
+            }
+        }
+
+        for (int i = 0; i < V - 1; i++) { // Algorithm loop - O(V)
+            for (int k = 0; k < graph.size(); k++) { // Edge loop - O(E)
+                Edge e = graph.get(k);
+                int u = e.src;
+                int v = e.dest;
+                int wt = e.wt;
+                if (dist[u] != Integer.MAX_VALUE && dist[u] + wt < dist[v]) { // Relaxation
+                    dist[v] = dist[u] + wt;
+                }
+            }
+        }
+        for (int i = 0; i < dist.length; i++) {
+            System.out.println("Source " + src + " to destination " + i + " Sorted path : " + dist[i]);
+        }
+    }
+
     public static void main(String[] args) {
         // Bellman Ford Algorithms --------------------------------
         // Shortest paths from the source to all vertices (Weighted Graph)
@@ -82,6 +136,12 @@ public static void main(String[] args) {
         createGraph(graph); // call for create graph
         int src = 0;
         bellmanFord(graph, src);
+        System.out.println();
+
+        // 2nd Sorted Method with sort code (Bellman Ford) --------------------------------
+        ArrayList<Edge> graph2 = new ArrayList<>();
+        createGraph2(graph2);
+        bellmanFord2(graph2, src, V);
     }
 
 }