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Remove print & main methods (#5584)

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This commit is contained in:
Hardik Pawar
2024-10-08 23:37:46 +05:30
committed by GitHub
parent ecd75c0c2e
commit d437d581f4
3 changed files with 81 additions and 32 deletions
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79
src/main/java/com/thealgorithms/datastructures/graphs/FloydWarshall.java
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@ -1,21 +1,46 @@
package com.thealgorithms.datastructures.graphs;
import java.util.Scanner;
/**
* The {@code FloydWarshall} class provides an implementation of the Floyd-Warshall algorithm
* to compute the shortest paths between all pairs of vertices in a weighted graph.
* It handles both positive and negative edge weights but does not support negative cycles.
* The algorithm is based on dynamic programming and runs in O(V^3) time complexity,
* where V is the number of vertices in the graph.
*
* <p>
* The distance matrix is updated iteratively to find the shortest distance between any two vertices
* by considering each vertex as an intermediate step.
* </p>
*
* Reference: <a href="https://en.wikipedia.org/wiki/Floyd%E2%80%93Warshall_algorithm">Floyd-Warshall Algorithm</a>
*/
public class FloydWarshall {
private int[][] distanceMatrix;
private int numberofvertices; // number of vertices in the graph
private int numberofvertices;
public static final int INFINITY = 999;
/**
* Constructs a Floyd-Warshall instance for a graph with the given number of vertices.
* Initializes the distance matrix for the graph.
*
* @param numberofvertices The number of vertices in the graph.
*/
public FloydWarshall(int numberofvertices) {
distanceMatrix = new int[numberofvertices + 1][numberofvertices + 1]; // stores the value of distance from all the possible path form the source
// vertex to destination vertex
distanceMatrix = new int[numberofvertices + 1][numberofvertices + 1];
// The matrix is initialized with 0's by default
this.numberofvertices = numberofvertices;
}
public void floydwarshall(int[][] adjacencyMatrix) { // calculates all the distances from source to destination vertex
/**
* Executes the Floyd-Warshall algorithm to compute the shortest path between all pairs of vertices.
* It uses an adjacency matrix to calculate the distance matrix by considering each vertex as an intermediate point.
*
* @param adjacencyMatrix The weighted adjacency matrix representing the graph.
* A value of 0 means no direct edge between the vertices, except for diagonal elements which are 0 (distance to self).
*/
public void floydwarshall(int[][] adjacencyMatrix) {
// Initialize the distance matrix with the adjacency matrix.
for (int source = 1; source <= numberofvertices; source++) {
for (int destination = 1; destination <= numberofvertices; destination++) {
distanceMatrix[source][destination] = adjacencyMatrix[source][destination];
@ -24,19 +49,29 @@ public class FloydWarshall {
for (int intermediate = 1; intermediate <= numberofvertices; intermediate++) {
for (int source = 1; source <= numberofvertices; source++) {
for (int destination = 1; destination <= numberofvertices; destination++) {
if (distanceMatrix[source][intermediate] + distanceMatrix[intermediate][destination] < distanceMatrix[source][destination]) { // calculated distance it get replaced as
// new shortest distance // if the new
// distance calculated is less then the
// earlier shortest
// Update distance if a shorter path through the intermediate vertex exists.
if (distanceMatrix[source][intermediate] + distanceMatrix[intermediate][destination] < distanceMatrix[source][destination]) {
distanceMatrix[source][destination] = distanceMatrix[source][intermediate] + distanceMatrix[intermediate][destination];
}
}
}
}
printDistanceMatrix();
}
/**
* Prints the distance matrix representing the shortest paths between all pairs of vertices.
* The rows and columns correspond to the source and destination vertices.
*/
private void printDistanceMatrix() {
// Print header for vertices
for (int source = 1; source <= numberofvertices; source++) {
System.out.print("\t" + source);
}
System.out.println();
// Print the distance matrix
for (int source = 1; source <= numberofvertices; source++) {
System.out.print(source + "\t");
for (int destination = 1; destination <= numberofvertices; destination++) {
@ -46,27 +81,7 @@ public class FloydWarshall {
}
}
public static void main(String... arg) {
Scanner scan = new Scanner(System.in);
System.out.println("Enter the number of vertices");
int numberOfVertices = scan.nextInt();
int[][] adjacencyMatrix = new int[numberOfVertices + 1][numberOfVertices + 1];
System.out.println("Enter the Weighted Matrix for the graph");
for (int source = 1; source <= numberOfVertices; source++) {
for (int destination = 1; destination <= numberOfVertices; destination++) {
adjacencyMatrix[source][destination] = scan.nextInt();
if (source == destination) {
adjacencyMatrix[source][destination] = 0;
continue;
}
if (adjacencyMatrix[source][destination] == 0) {
adjacencyMatrix[source][destination] = INFINITY;
}
}
}
System.out.println("The Transitive Closure of the Graph");
FloydWarshall floydwarshall = new FloydWarshall(numberOfVertices);
floydwarshall.floydwarshall(adjacencyMatrix);
scan.close();
public Object[] getDistanceMatrix() {
return distanceMatrix;
}
}