Java Program to Implement Floyd-Warshall Algorithm

This Java program is to implement the Floyd-Warshall algorithm.The algorithm is a graph analysis algorithm for finding shortest paths in a weighted graph with positive or negative edge weights (but with no negative cycles) and also for finding transitive closure of a relation R.

Here is the source code of the Java program to implement Floyd-Warshall algorithm. The Java program is successfully compiled and run on a Linux system. The program output is also shown below.

  1. import java.util.Scanner;
  2.  
  3. public class FloydWarshall
  4. {
  5.     private int distancematrix[][];
  6.     private int numberofvertices;
  7.     public static final int INFINITY = 999;
  8.  
  9.     public FloydWarshall(int numberofvertices)
  10.     {
  11.         distancematrix = new int[numberofvertices + 1][numberofvertices + 1];
  12.         this.numberofvertices = numberofvertices;
  13.     }
  14.  
  15.     public void floydwarshall(int adjacencymatrix[][])
  16.     {
  17.         for (int source = 1; source <= numberofvertices; source++)
  18.         {
  19.             for (int destination = 1; destination <= numberofvertices; destination++)
  20.             {
  21.                 distancematrix[source][destination] = adjacencymatrix[source][destination];
  22.             }
  23.         }
  24.  
  25.         for (int intermediate = 1; intermediate <= numberofvertices; intermediate++)
  26.         {
  27.             for (int source = 1; source <= numberofvertices; source++)
  28.             {
  29.                 for (int destination = 1; destination <= numberofvertices; destination++)
  30.                 {
  31.                     if (distancematrix[source][intermediate] + distancematrix[intermediate][destination]
  32.                          < distancematrix[source][destination])
  33.                         distancematrix[source][destination] = distancematrix[source][intermediate] 
  34.                             + distancematrix[intermediate][destination];
  35.                 }
  36.             }
  37.         }
  38.  
  39.         for (int source = 1; source <= numberofvertices; source++)
  40.             System.out.print("\t" + source);
  41.  
  42.         System.out.println();
  43.         for (int source = 1; source <= numberofvertices; source++)
  44.         {
  45.             System.out.print(source + "\t");
  46.             for (int destination = 1; destination <= numberofvertices; destination++)
  47.             {
  48.                 System.out.print(distancematrix[source][destination] + "\t");
  49.             }
  50.             System.out.println();
  51.         }
  52.     }
  53.  
  54.     public static void main(String... arg)
  55.     {
  56.         int adjacency_matrix[][];
  57.         int numberofvertices;
  58.  
  59.         Scanner scan = new Scanner(System.in);
  60.         System.out.println("Enter the number of vertices");
  61.         numberofvertices = scan.nextInt();
  62.  
  63.         adjacency_matrix = new int[numberofvertices + 1][numberofvertices + 1];
  64.         System.out.println("Enter the Weighted Matrix for the graph");
  65.         for (int source = 1; source <= numberofvertices; source++)
  66.         {
  67.             for (int destination = 1; destination <= numberofvertices; destination++)
  68.             {
  69.                 adjacency_matrix[source][destination] = scan.nextInt();
  70.                 if (source == destination)
  71.                 {
  72.                     adjacency_matrix[source][destination] = 0;
  73.                     continue;
  74.                 }
  75.                 if (adjacency_matrix[source][destination] == 0)
  76.                 {
  77.                     adjacency_matrix[source][destination] = INFINITY;
  78.                 }
  79.             }
  80.         }
  81.  
  82.         System.out.println("The Transitive Closure of the Graph");
  83.         FloydWarshall floydwarshall = new FloydWarshall(numberofvertices);
  84.         floydwarshall.floydwarshall(adjacency_matrix);
  85.         scan.close();
  86.     }
  87. }

$javac FloydWarshall.java
$java FloydWarshall 
 
Enter the number of vertices
4
 
Enter the Weighted Matrix for the graph
0 0 3 0
2 0 0 0 
0 7 0 1
6 0 0 0
 
The Transitive Closure of the Graph
 
	1	2	3	4
1	0	10	3	4	
2	2	0	5	6	
3	7	7	0	1	
4	6	16	9	0

If you find any mistake above, kindly email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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