105 lines
4.6 KiB
Java
105 lines
4.6 KiB
Java
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/*This is a java program to find shortest path between all vertices using FLoyd-Warshall’s algorithm. In computer science, the Floyd–Warshall algorithm (also known as Floyd’s algorithm, Roy–Warshall algorithm, Roy–Floyd algorithm, or the WFI 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, see below) and also for finding transitive closure of a relation R. A single execution of the algorithm will find the lengths (summed weights) of the shortest paths between all pairs of vertices, though it does not return details of the paths themselves.*/
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import java.util.Scanner;
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public class FloydWarshallShortestPath
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{
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private int distancematrix[][];
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private int numberofvertices;
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public static final int INFINITY = 999;
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public FloydWarshallShortestPath(int numberofvertices)
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{
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distancematrix = new int[numberofvertices + 1][numberofvertices + 1];
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this.numberofvertices = numberofvertices;
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}
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public void floydwarshall(int adjacencymatrix[][])
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{
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for (int source = 1; source <= numberofvertices; source++)
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{
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for (int destination = 1; destination <= numberofvertices; destination++)
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{
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distancematrix[source][destination] = adjacencymatrix[source][destination];
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}
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}
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for (int intermediate = 1; intermediate <= numberofvertices; intermediate++)
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{
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for (int source = 1; source <= numberofvertices; source++)
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{
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for (int destination = 1; destination <= numberofvertices; destination++)
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{
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if (distancematrix[source][intermediate]
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+ distancematrix[intermediate][destination] < distancematrix[source][destination])
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distancematrix[source][destination] = distancematrix[source][intermediate]
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+ distancematrix[intermediate][destination];
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}
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}
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}
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for (int source = 1; source <= numberofvertices; source++)
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System.out.print("\t" + source);
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System.out.println();
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for (int source = 1; source <= numberofvertices; source++)
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{
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System.out.print(source + "\t");
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for (int destination = 1; destination <= numberofvertices; destination++)
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{
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System.out.print(distancematrix[source][destination] + "\t");
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}
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System.out.println();
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}
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}
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public static void main(String... arg)
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{
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int adjacency_matrix[][];
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int numberofvertices;
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Scanner scan = new Scanner(System.in);
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System.out.println("Enter the number of vertices");
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numberofvertices = scan.nextInt();
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adjacency_matrix = new int[numberofvertices + 1][numberofvertices + 1];
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System.out.println("Enter the Weighted Matrix for the graph");
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for (int source = 1; source <= numberofvertices; source++)
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{
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for (int destination = 1; destination <= numberofvertices; destination++)
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{
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adjacency_matrix[source][destination] = scan.nextInt();
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if (source == destination)
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{
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adjacency_matrix[source][destination] = 0;
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continue;
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}
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if (adjacency_matrix[source][destination] == 0)
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{
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adjacency_matrix[source][destination] = INFINITY;
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}
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}
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}
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System.out.println("The Transitive Closure of the Graph");
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FloydWarshallShortestPath floydwarshall = new FloydWarshallShortestPath(
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numberofvertices);
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floydwarshall.floydwarshall(adjacency_matrix);
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scan.close();
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}
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}
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/*
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Enter the number of vertices
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6
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Enter the Weighted Matrix for the graph
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0 4 0 0 1 0
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0 0 1 0 2 0
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0 0 0 0 0 0
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0 0 0 0 0 0
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0 0 0 5 0 3
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0 0 0 0 0 0
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The Transitive Closure of the Graph (999 represents not reachable)
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1 2 3 4 5 6
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1 0 4 5 6 1 4
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2 999 0 1 7 2 5
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3 999 999 0 999 999 999
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4 999 999 999 0 999 999
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5 999 999 999 5 0 3
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6 999 999 999 999 999 0
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