Merge branch 'master' into workflow/close-failed-prs

Author: DenizAltunkapan

DIRECTORY.md

@@ -173,6 +173,7 @@
             - 📄 [FordFulkerson](src/main/java/com/thealgorithms/datastructures/graphs/FordFulkerson.java)
             - 📄 [Graphs](src/main/java/com/thealgorithms/datastructures/graphs/Graphs.java)
             - 📄 [HamiltonianCycle](src/main/java/com/thealgorithms/datastructures/graphs/HamiltonianCycle.java)
+            - 📄 [HierholzerAlgorithm](src/main/java/com/thealgorithms/graph/HierholzerAlgorithm.java)
             - 📄 [JohnsonsAlgorithm](src/main/java/com/thealgorithms/datastructures/graphs/JohnsonsAlgorithm.java)
             - 📄 [KahnsAlgorithm](src/main/java/com/thealgorithms/datastructures/graphs/KahnsAlgorithm.java)
             - 📄 [Kosaraju](src/main/java/com/thealgorithms/datastructures/graphs/Kosaraju.java)

pom.xml

@@ -20,7 +20,7 @@
             <dependency>
                 <groupId>org.junit</groupId>
                 <artifactId>junit-bom</artifactId>
-                <version>6.0.0</version>
+                <version>6.0.1</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>

src/main/java/com/thealgorithms/bitmanipulation/BitRotate.java

@@ -0,0 +1,83 @@
+package com.thealgorithms.bitmanipulation;
+
+/**
+ * Utility class for performing circular bit rotations on 32-bit integers.
+ * Bit rotation is a circular shift operation where bits shifted out on one end
+ * are reinserted on the opposite end.
+ *
+ * <p>This class provides methods for both left and right circular rotations,
+ * supporting only 32-bit integer operations with proper shift normalization
+ * and error handling.</p>
+ *
+ * @see <a href="https://en.wikipedia.org/wiki/Bit_rotation">Bit Rotation</a>
+ */
+public final class BitRotate {
+
+    /**
+     * Private constructor to prevent instantiation.
+     * This is a utility class with only static methods.
+     */
+    private BitRotate() {
+        throw new UnsupportedOperationException("This is a utility class and cannot be instantiated");
+    }
+
+    /**
+     * Performs a circular left rotation (left shift) on a 32-bit integer.
+     * Bits shifted out from the left side are inserted on the right side.
+     *
+     * @param value the 32-bit integer value to rotate
+     * @param shift the number of positions to rotate left (must be non-negative)
+     * @return the result of left rotating the value by the specified shift amount
+     * @throws IllegalArgumentException if shift is negative
+     *
+     * @example
+     * // Binary: 10000000 00000000 00000000 00000001
+     * rotateLeft(0x80000001, 1)
+     * // Returns: 3 (binary: 00000000 00000000 00000000 00000011)
+     */
+    public static int rotateLeft(int value, int shift) {
+        if (shift < 0) {
+            throw new IllegalArgumentException("Shift amount cannot be negative: " + shift);
+        }
+
+        // Normalize shift to the range [0, 31] using modulo 32
+        shift = shift % 32;
+
+        if (shift == 0) {
+            return value;
+        }
+
+        // Left rotation: (value << shift) | (value >>> (32 - shift))
+        return (value << shift) | (value >>> (32 - shift));
+    }
+
+    /**
+     * Performs a circular right rotation (right shift) on a 32-bit integer.
+     * Bits shifted out from the right side are inserted on the left side.
+     *
+     * @param value the 32-bit integer value to rotate
+     * @param shift the number of positions to rotate right (must be non-negative)
+     * @return the result of right rotating the value by the specified shift amount
+     * @throws IllegalArgumentException if shift is negative
+     *
+     * @example
+     * // Binary: 00000000 00000000 00000000 00000011
+     * rotateRight(3, 1)
+     * // Returns: -2147483647 (binary: 10000000 00000000 00000000 00000001)
+     */
+    public static int rotateRight(int value, int shift) {
+        if (shift < 0) {
+            throw new IllegalArgumentException("Shift amount cannot be negative: " + shift);
+        }
+
+        // Normalize shift to the range [0, 31] using modulo 32
+        shift = shift % 32;
+
+        if (shift == 0) {
+            return value;
+        }
+
+        // Right rotation: (value >>> shift) | (value << (32 - shift))
+        return (value >>> shift) | (value << (32 - shift));
+    }
+}

src/main/java/com/thealgorithms/graph/HierholzerAlgorithm.java

@@ -0,0 +1,140 @@
+package com.thealgorithms.graph;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.Stack;
+
+/**
+ * Implementation of Hierholzer's algorithm to find an Eulerian Circuit in an undirected graph.
+ * <p>
+ * An Eulerian circuit is a trail in a graph that visits every edge exactly once,
+ * starting and ending at the same vertex. This algorithm finds such a circuit if one exists.
+ * </p>
+ * <p>
+ * This implementation is designed for an <strong>undirected graph</strong>. For a valid Eulerian
+ * circuit to exist, the graph must satisfy two conditions:
+ * <ol>
+ * <li>All vertices with a non-zero degree must be part of a single connected component.</li>
+ * <li>Every vertex must have an even degree (an even number of edges connected to it).</li>
+ * </ol>
+ * </p>
+ * <p>
+ * The algorithm runs in O(E + V) time, where E is the number of edges and V is the number of vertices.
+ * The graph is represented by a Map where keys are vertices and values are a LinkedList of adjacent vertices.
+ * </p>
+ *
+ * @see <a href="https://en.wikipedia.org/wiki/Eulerian_path#Hierholzer's_algorithm">Wikipedia: Hierholzer's algorithm</a>
+ */
+public final class HierholzerAlgorithm {
+
+    private final Map<Integer, LinkedList<Integer>> graph;
+
+    public HierholzerAlgorithm(Map<Integer, LinkedList<Integer>> graph) {
+        this.graph = (graph == null) ? new HashMap<>() : graph;
+    }
+
+    public boolean hasEulerianCircuit() {
+        if (graph.isEmpty()) {
+            return true;
+        }
+
+        for (List<Integer> neighbors : graph.values()) {
+            if (neighbors.size() % 2 != 0) {
+                return false;
+            }
+        }
+
+        return isCoherentlyConnected();
+    }
+
+    public List<Integer> findEulerianCircuit() {
+        if (!hasEulerianCircuit()) {
+            return Collections.emptyList();
+        }
+
+        Map<Integer, LinkedList<Integer>> tempGraph = new HashMap<>();
+        for (Map.Entry<Integer, LinkedList<Integer>> entry : graph.entrySet()) {
+            tempGraph.put(entry.getKey(), new LinkedList<>(entry.getValue()));
+        }
+
+        Stack<Integer> currentPath = new Stack<>();
+        LinkedList<Integer> circuit = new LinkedList<>();
+
+        int startVertex = -1;
+        for (Map.Entry<Integer, LinkedList<Integer>> entry : tempGraph.entrySet()) {
+            if (!entry.getValue().isEmpty()) {
+                startVertex = entry.getKey();
+                break;
+            }
+        }
+
+        if (startVertex == -1) {
+            if (graph.isEmpty()) {
+                return Collections.emptyList();
+            }
+            return Collections.singletonList(graph.keySet().iterator().next());
+        }
+
+        currentPath.push(startVertex);
+
+        while (!currentPath.isEmpty()) {
+            int currentVertex = currentPath.peek();
+
+            if (tempGraph.containsKey(currentVertex) && !tempGraph.get(currentVertex).isEmpty()) {
+                int nextVertex = tempGraph.get(currentVertex).pollFirst();
+                tempGraph.get(nextVertex).remove(Integer.valueOf(currentVertex));
+                currentPath.push(nextVertex);
+            } else {
+                circuit.addFirst(currentVertex);
+                currentPath.pop();
+            }
+        }
+
+        return circuit;
+    }
+
+    private boolean isCoherentlyConnected() {
+        if (graph.isEmpty()) {
+            return true;
+        }
+
+        Set<Integer> visited = new HashSet<>();
+        int startNode = -1;
+
+        for (Map.Entry<Integer, LinkedList<Integer>> entry : graph.entrySet()) {
+            if (!entry.getValue().isEmpty()) {
+                startNode = entry.getKey();
+                break;
+            }
+        }
+
+        if (startNode == -1) {
+            return true;
+        }
+
+        dfs(startNode, visited);
+
+        for (Map.Entry<Integer, LinkedList<Integer>> entry : graph.entrySet()) {
+            if (!entry.getValue().isEmpty() && !visited.contains(entry.getKey())) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private void dfs(int u, Set<Integer> visited) {
+        visited.add(u);
+        if (graph.containsKey(u)) {
+            for (int v : graph.get(u)) {
+                if (!visited.contains(v)) {
+                    dfs(v, visited);
+                }
+            }
+        }
+    }
+}

src/main/java/com/thealgorithms/maths/Area.java

@@ -48,6 +48,25 @@ public static double surfaceAreaSphere(final double radius) {
         return 4 * Math.PI * radius * radius;
     }
 
+    /**
+     * Calculate the surface area of a pyramid with a square base.
+     *
+     * @param sideLength side length of the square base
+     * @param slantHeight slant height of the pyramid
+     * @return surface area of the given pyramid
+     */
+    public static double surfaceAreaPyramid(final double sideLength, final double slantHeight) {
+        if (sideLength <= 0) {
+            throw new IllegalArgumentException("Must be a positive sideLength");
+        }
+        if (slantHeight <= 0) {
+            throw new IllegalArgumentException("Must be a positive slantHeight");
+        }
+        double baseArea = sideLength * sideLength;
+        double lateralSurfaceArea = 2 * sideLength * slantHeight;
+        return baseArea + lateralSurfaceArea;
+    }
+
     /**
      * Calculate the area of a rectangle.
      *

src/main/java/com/thealgorithms/maths/JugglerSequence.java

@@ -43,7 +43,7 @@ public static void jugglerSequence(int inputNumber) {
             seq.add(n + "");
         }
         String res = String.join(",", seq);
-        System.out.println(res);
+        System.out.print(res + "\n");
     }
 
     // Driver code

src/main/java/com/thealgorithms/matrix/LUDecomposition.java

@@ -0,0 +1,88 @@
+package com.thealgorithms.matrix;
+
+/**
+ * LU Decomposition algorithm
+ * --------------------------
+ * Decomposes a square matrix a into a product of two matrices:
+ * a = l * u
+ * where:
+ * - l is a lower triangular matrix with 1s on its diagonal
+ * - u is an upper triangular matrix
+ *
+ * Reference:
+ * https://en.wikipedia.org/wiki/lu_decomposition
+ */
+public final class LUDecomposition {
+
+    private LUDecomposition() {
+    }
+
+    /**
+     * A helper class to store both l and u matrices
+     */
+    public static class LU {
+        double[][] l;
+        double[][] u;
+
+        LU(double[][] l, double[][] u) {
+            this.l = l;
+            this.u = u;
+        }
+    }
+
+    /**
+     * Performs LU Decomposition on a square matrix a
+     *
+     * @param a input square matrix
+     * @return LU object containing l and u matrices
+     */
+    public static LU decompose(double[][] a) {
+        int n = a.length;
+        double[][] l = new double[n][n];
+        double[][] u = new double[n][n];
+
+        for (int i = 0; i < n; i++) {
+            // upper triangular matrix
+            for (int k = i; k < n; k++) {
+                double sum = 0;
+                for (int j = 0; j < i; j++) {
+                    sum += l[i][j] * u[j][k];
+                }
+                u[i][k] = a[i][k] - sum;
+            }
+
+            // lower triangular matrix
+            for (int k = i; k < n; k++) {
+                if (i == k) {
+                    l[i][i] = 1; // diagonal as 1
+                } else {
+                    double sum = 0;
+                    for (int j = 0; j < i; j++) {
+                        sum += l[k][j] * u[j][i];
+                    }
+                    l[k][i] = (a[k][i] - sum) / u[i][i];
+                }
+            }
+        }
+
+        return new LU(l, u);
+    }
+
+    /**
+     * Utility function to print a matrix
+     *
+     * @param m matrix to print
+     */
+    public static void printMatrix(double[][] m) {
+        for (double[] row : m) {
+            System.out.print("[");
+            for (int j = 0; j < row.length; j++) {
+                System.out.printf("%7.3f", row[j]);
+                if (j < row.length - 1) {
+                    System.out.print(", ");
+                }
+            }
+            System.out.println("]");
+        }
+    }
+}