From d437d581f4d280f632e663fc528e0a9c2605cbf4 Mon Sep 17 00:00:00 2001 From: Hardik Pawar <97388607+Hardvan@users.noreply.github.com> Date: Tue, 8 Oct 2024 23:37:46 +0530 Subject: [PATCH] Remove `print` & `main` methods (#5584) --- DIRECTORY.md | 1 + .../datastructures/graphs/FloydWarshall.java | 79 +++++++++++-------- .../graphs/FloydWarshallTest.java | 33 ++++++++ 3 files changed, 81 insertions(+), 32 deletions(-) create mode 100644 src/test/java/com/thealgorithms/datastructures/graphs/FloydWarshallTest.java diff --git a/DIRECTORY.md b/DIRECTORY.md index 7c6f284c9..6042dd1b5 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -709,6 +709,7 @@ * [BoruvkaAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/BoruvkaAlgorithmTest.java) * [DijkstraAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/DijkstraAlgorithmTest.java) * [EdmondsBlossomAlgorithmTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/EdmondsBlossomAlgorithmTest.java) + * [FloydWarshallTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/FloydWarshallTest.java) * [FordFulkersonTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/FordFulkersonTest.java) * [HamiltonianCycleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/HamiltonianCycleTest.java) * [KosarajuTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/graphs/KosarajuTest.java) diff --git a/src/main/java/com/thealgorithms/datastructures/graphs/FloydWarshall.java b/src/main/java/com/thealgorithms/datastructures/graphs/FloydWarshall.java index d47ffe3aa..66dc6782a 100644 --- a/src/main/java/com/thealgorithms/datastructures/graphs/FloydWarshall.java +++ b/src/main/java/com/thealgorithms/datastructures/graphs/FloydWarshall.java @@ -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. + * + *

+ * The distance matrix is updated iteratively to find the shortest distance between any two vertices + * by considering each vertex as an intermediate step. + *

+ * + * Reference: Floyd-Warshall Algorithm + */ 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; } } diff --git a/src/test/java/com/thealgorithms/datastructures/graphs/FloydWarshallTest.java b/src/test/java/com/thealgorithms/datastructures/graphs/FloydWarshallTest.java new file mode 100644 index 000000000..7d6a2b239 --- /dev/null +++ b/src/test/java/com/thealgorithms/datastructures/graphs/FloydWarshallTest.java @@ -0,0 +1,33 @@ +package com.thealgorithms.datastructures.graphs; + +import static org.junit.jupiter.api.Assertions.assertArrayEquals; + +import org.junit.jupiter.api.Test; + +class FloydWarshallTest { + + @Test + void testSmallGraph() { + int[][] adjacencyMatrix = {{0, 0, 0, 0}, // Ignored row (0 index) + {0, 0, 3, FloydWarshall.INFINITY}, {0, FloydWarshall.INFINITY, 0, 1}, {0, FloydWarshall.INFINITY, FloydWarshall.INFINITY, 0}}; + + FloydWarshall fw = new FloydWarshall(3); + fw.floydwarshall(adjacencyMatrix); + + int[][] expectedDistanceMatrix = {{0, 0, 0, 0}, {0, 0, 3, 4}, {0, FloydWarshall.INFINITY, 0, 1}, {0, FloydWarshall.INFINITY, FloydWarshall.INFINITY, 0}}; + + assertArrayEquals(expectedDistanceMatrix, fw.getDistanceMatrix()); + } + + @Test + void testLargerGraph() { + int[][] adjacencyMatrix = {{0, 0, 0, 0, 0}, {0, 0, 1, FloydWarshall.INFINITY, 2}, {0, FloydWarshall.INFINITY, 0, 4, FloydWarshall.INFINITY}, {0, FloydWarshall.INFINITY, FloydWarshall.INFINITY, 0, 3}, {0, FloydWarshall.INFINITY, FloydWarshall.INFINITY, FloydWarshall.INFINITY, 0}}; + + FloydWarshall fw = new FloydWarshall(4); + fw.floydwarshall(adjacencyMatrix); + + int[][] expectedDistanceMatrix = {{0, 0, 0, 0, 0}, {0, 0, 1, 5, 2}, {0, FloydWarshall.INFINITY, 0, 4, 7}, {0, FloydWarshall.INFINITY, FloydWarshall.INFINITY, 0, 3}, {0, FloydWarshall.INFINITY, FloydWarshall.INFINITY, FloydWarshall.INFINITY, 0}}; + + assertArrayEquals(expectedDistanceMatrix, fw.getDistanceMatrix()); + } +}