Create Prims.java

Graphs/Pims.java

@@ -0,0 +1,105 @@
+import java.util.*; 
+import java.lang.*; 
+import java.io.*; 
+
+class MST { 
+    // Number of vertices in the graph 
+    private static final int V = 5; 
+
+    // A utility function to find the vertex with minimum key 
+    // value, from the set of vertices not yet included in MST 
+    int minKey(int key[], Boolean mstSet[]) 
+    { 
+        // Initialize min value 
+        int min = Integer.MAX_VALUE, min_index = -1; 
+
+        for (int v = 0; v < V; v++) 
+            if (mstSet[v] == false && key[v] < min) { 
+                min = key[v]; 
+                min_index = v; 
+            } 
+
+        return min_index; 
+    } 
+
+    // A utility function to print the constructed MST stored in 
+    // parent[] 
+    void printMST(int parent[], int graph[][]) 
+    { 
+        System.out.println("Edge \tWeight"); 
+        for (int i = 1; i < V; i++) 
+            System.out.println(parent[i] + " - " + i + "\t" + graph[i][parent[i]]); 
+    } 
+
+    // Function to construct and print MST for a graph represented 
+    // using adjacency matrix representation 
+    void primMST(int graph[][]) 
+    { 
+        // Array to store constructed MST 
+        int parent[] = new int[V]; 
+
+        // Key values used to pick minimum weight edge in cut 
+        int key[] = new int[V]; 
+
+        // To represent set of vertices not yet included in MST 
+        Boolean mstSet[] = new Boolean[V]; 
+
+        // Initialize all keys as INFINITE 
+        for (int i = 0; i < V; i++) { 
+            key[i] = Integer.MAX_VALUE; 
+            mstSet[i] = false; 
+        } 
+
+        // Always include first 1st vertex in MST. 
+        key[0] = 0; // Make key 0 so that this vertex is 
+        // picked as first vertex 
+        parent[0] = -1; // First node is always root of MST 
+
+        // The MST will have V vertices 
+        for (int count = 0; count < V - 1; count++) { 
+            // Pick thd minimum key vertex from the set of vertices 
+            // not yet included in MST 
+            int u = minKey(key, mstSet); 
+
+            // Add the picked vertex to the MST Set 
+            mstSet[u] = true; 
+
+            // Update key value and parent index of the adjacent 
+            // vertices of the picked vertex. Consider only those 
+            // vertices which are not yet included in MST 
+            for (int v = 0; v < V; v++) 
+
+                // graph[u][v] is non zero only for adjacent vertices of m 
+                // mstSet[v] is false for vertices not yet included in MST 
+                // Update the key only if graph[u][v] is smaller than key[v] 
+                if (graph[u][v] != 0 && mstSet[v] == false && graph[u][v] < key[v]) { 
+                    parent[v] = u; 
+                    key[v] = graph[u][v]; 
+                } 
+        } 
+
+        // print the constructed MST 
+        printMST(parent, graph); 
+    } 
+
+    public static void main(String[] args) 
+    { 
+        /* Let us create the following graph 
+        2 3 
+        (0)--(1)--(2) 
+        | / \ | 
+        6| 8/ \5 |7 
+        | /     \ | 
+        (3)-------(4) 
+            9         */
+        MST t = new MST(); 
+        int graph[][] = new int[][] { { 0, 2, 0, 6, 0 }, 
+                                      { 2, 0, 3, 8, 5 }, 
+                                      { 0, 3, 0, 0, 7 }, 
+                                      { 6, 8, 0, 0, 9 }, 
+                                      { 0, 5, 7, 9, 0 } }; 
+
+        // Print the solution 
+        t.primMST(graph); 
+    } 
+}