Create prims.java

prims.java

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+package javaproject;                                                                                                                        
+
+
+
+// Prim's Algorithm in Java                                                                                                                 
+import java.util.Arrays;                                                                                                                    
+
+class prims {                                                                                                                               
+
+  public void Prim(int G[][], int V) {                                                                                                      
+
+    int INF = 9999999;                                                                                                                      
+
+    int no_edge; // number of edge                                                                                                          
+
+    // create a array to track selected vertex                                                                                              
+    // selected will become true otherwise false                                                                                            
+    boolean[] selected = new boolean[V];                                                                                                    
+
+    // set selected false initially                                                                                                         
+    Arrays.fill(selected, false);                                                                                                           
+
+    // set number of edge to 0                                                                                                              
+    no_edge = 0;                                                                                                                            
+
+    // the number of egde in minimum spanning tree will be                                                                                  
+    // always less than (V -1), where V is number of vertices in                                                                            
+    // graph                                                                                                                                
+
+    // choose 0th vertex and make it true                                                                                                   
+    selected[0] = true;                                                                                                                     
+
+    // print for edge and weight                                                                                                            
+    System.out.println("Edge : Weight");                                                                                                    
+
+    while (no_edge < V - 1) {                                                                                                               
+      // For every vertex in the set S, find the all adjacent vertices                                                                      
+      // , calculate the distance from the vertex selected at step 1.                                                                       
+      // if the vertex is already in the set S, discard it otherwise                                                                        
+      // choose another vertex nearest to selected vertex at step 1.                                                                        
+
+      int min = INF;                                                                                                                        
+      int x = 0; // row number                                                                                                              
+      int y = 0; // col number                                                                                                              
+
+      for (int i = 0; i < V; i++) {                                                                                                         
+        if (selected[i] == true) {                                                                                                          
+          for (int j = 0; j < V; j++) {                                                                                                     
+            // not in selected and there is an edge                                                                                         
+            if (!selected[j] && G[i][j] != 0) {                                                                                             
+              if (min > G[i][j]) {                                                                                                          
+                min = G[i][j];                                                                                                              
+                x = i;                                                                                                                      
+                y = j;                                                                                                                      
+              }                                                                                                                             
+            }                                                                                                                               
+          }                                                                                                                                 
+        }                                                                                                                                   
+      }                                                                                                                                     
+      System.out.println(x + " - " + y + " :  " + G[x][y]);                                                                                 
+      selected[y] = true;                                                                                                                   
+      no_edge++;                                                                                                                            
+    }                                                                                                                                       
+  }                                                                                                                                         
+
+  public static void main(String[] args) {                                                                                                  
+    prims g = new prims();                                                                                                                  
+
+    // number of vertices in grapj                                                                                                          
+    int V = 5;                                                                                                                              
+
+    // create a 2d array of size 5x5                                                                                                        
+    // for adjacency matrix to represent graph                                                                                              
+    int[][] G = { { 0, 9, 75, 0, 0 }, { 9, 0, 95, 19, 42 }, { 75, 95, 0, 51, 66 }, { 0, 19, 51, 0, 31 },                                    
+        { 0, 42, 66, 31, 0 } };                                                                                                             
+
+    g.Prim(G, V);                                                                                                                           
+  }                                                                                                                                         
+}                                                                                                                                           
+
+//output
+/*
+Edge : Weight
+0 - 1 :  9
+1 - 3 :  19
+3 - 4 :  31
+3 - 2 :  51
+
+
+*/