Merge branch 'master' into master

Author: siriak

DIRECTORY.md

@@ -982,6 +982,7 @@
             * [JosephusProblemTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/JosephusProblemTest.java)
             * [KaprekarNumbersTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/KaprekarNumbersTest.java)
             * [KaratsubaMultiplicationTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/KaratsubaMultiplicationTest.java)
+            * [KrishnamurthyNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/KrishnamurthyNumberTest.java)
             * [LeastCommonMultipleTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/LeastCommonMultipleTest.java)
             * [LeonardoNumberTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/LeonardoNumberTest.java)
             * [LiouvilleLambdaFunctionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/maths/LiouvilleLambdaFunctionTest.java)

src/main/java/com/thealgorithms/dynamicprogramming/RodCutting.java

@@ -22,6 +22,10 @@ public static int cutRod(int[] price, int n) {
         if (price == null || price.length == 0) {
             throw new IllegalArgumentException("Price array cannot be null or empty.");
         }
+        if (n < 0) {
+            throw new IllegalArgumentException("Rod length cannot be negative.");
+        }
+
         // Create an array to store the maximum obtainable values for each rod length.
         int[] val = new int[n + 1];
         val[0] = 0;

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

@@ -1,9 +1,23 @@
 package com.thealgorithms.maths;
 
 /**
- * This is Euclid's algorithm, used to find the greatest common
- * denominator Override function name gcd
+ *  This class provides methods to compute the Greatest Common Divisor (GCD) of two or more integers.
  *
+ * The Greatest Common Divisor (GCD) of two or more integers is the largest positive integer that divides each of the integers without leaving a remainder.
+ *
+ * The GCD can be computed using the Euclidean algorithm, which is based on the principle that the GCD of two numbers also divides their difference.
+ *
+ * For more information, refer to the
+ * <a href="https://en.wikipedia.org/wiki/Greatest_common_divisor">Greatest Common Divisor</a> Wikipedia page.
+ *
+ * <b>Example usage:</b>
+ * <pre>
+ * int result1 = GCD.gcd(48, 18);
+ * System.out.println("GCD of 48 and 18: " + result1); // Output: 6
+ *
+ * int result2 = GCD.gcd(48, 18, 30);
+ * System.out.println("GCD of 48, 18, and 30: " + result2); // Output: 6
+ * </pre>
  * @author Oskar Enmalm 3/10/17
  */
 public final class GCD {
@@ -40,20 +54,12 @@ public static int gcd(int num1, int num2) {
      * @param numbers the input array
      * @return gcd of all of the numbers in the input array
      */
-    public static int gcd(int[] numbers) {
+    public static int gcd(int... numbers) {
         int result = 0;
         for (final var number : numbers) {
             result = gcd(result, number);
         }
 
         return result;
     }
-
-    public static void main(String[] args) {
-        int[] myIntArray = {4, 16, 32};
-
-        // call gcd function (input array)
-        System.out.println(gcd(myIntArray)); // => 4
-        System.out.printf("gcd(40,24)=%d gcd(24,40)=%d%n", gcd(40, 24), gcd(24, 40)); // => 8
-    }
 }

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

@@ -1,31 +1,38 @@
 package com.thealgorithms.maths;
 
-/* This is a program to check if a number is a Krishnamurthy number or not.
-A number is a Krishnamurthy number if the sum of the factorials of the digits of the number is equal
-to the number itself. For example, 1, 2 and 145 are Krishnamurthy numbers. Krishnamurthy number is
-also referred to as a Strong number.
+/**
+ * Utility class for checking if a number is a Krishnamurthy number.
+ *
+ * A Krishnamurthy number (also known as a Strong number) is a number whose sum of the factorials of its digits is equal to the number itself.
+ *
+ * For example, 145 is a Krishnamurthy number because 1! + 4! + 5! = 1 + 24 + 120 = 145.
+ * <b>Example usage:</b>
+ * <pre>
+ * boolean isKrishnamurthy = KrishnamurthyNumber.isKrishnamurthy(145);
+ * System.out.println(isKrishnamurthy); // Output: true
+ *
+ * isKrishnamurthy = KrishnamurthyNumber.isKrishnamurthy(123);
+ * System.out.println(isKrishnamurthy); // Output: false
+ * </pre>
  */
-import java.io.BufferedReader;
-import java.io.IOException;
-import java.io.InputStreamReader;
-
 public final class KrishnamurthyNumber {
+
     private KrishnamurthyNumber() {
     }
 
-    // returns True if the number is a Krishnamurthy number and False if it is not.
-
-    public static boolean isKMurthy(int n) {
-        // initialising the variable s that will store the sum of the factorials of the digits to 0
-        int s = 0;
-        // storing the number n in a temporary variable tmp
+    /**
+     * Checks if a number is a Krishnamurthy number.
+     *
+     * @param n The number to check
+     * @return true if the number is a Krishnamurthy number, false otherwise
+     */
+    public static boolean isKrishnamurthy(int n) {
         int tmp = n;
+        int s = 0;
 
-        // Krishnamurthy numbers are positive
         if (n <= 0) {
             return false;
-        } // checking if the number is a Krishnamurthy number
-        else {
+        } else {
             while (n != 0) {
                 // initialising the variable fact that will store the factorials of the digits
                 int fact = 1;
@@ -43,15 +50,4 @@ public static boolean isKMurthy(int n) {
             return tmp == s;
         }
     }
-
-    public static void main(String[] args) throws IOException {
-        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
-        System.out.println("Enter a number to check if it is a Krishnamurthy number: ");
-        int n = Integer.parseInt(br.readLine());
-        if (isKMurthy(n)) {
-            System.out.println(n + " is a Krishnamurthy number.");
-        } else {
-            System.out.println(n + " is NOT a Krishnamurthy number.");
-        }
-    }
 }

src/main/java/com/thealgorithms/searches/BreadthFirstSearch.java

@@ -3,37 +3,54 @@
 import com.thealgorithms.datastructures.Node;
 import java.util.ArrayDeque;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Optional;
 import java.util.Queue;
+import java.util.Set;
 
 /**
- * @author: caos321
- * @date: 31 October 2021 (Sunday)
- * @wiki: https://en.wikipedia.org/wiki/Breadth-first_search
+ * Breadth-First Search implementation for tree/graph traversal.
+ * @author caos321
+ * @co-author @manishraj27
+ * @see <a href="https://en.wikipedia.org/wiki/Breadth-first_search">Breadth-first search</a>
  */
 public class BreadthFirstSearch<T> {
-
     private final List<T> visited = new ArrayList<>();
+    private final Set<T> visitedSet = new HashSet<>();
 
-    public Optional<Node<T>> search(final Node<T> node, final T value) {
-        if (node == null) {
+    /**
+     * Performs a breadth-first search to find a node with the given value.
+     *
+     * @param root The root node to start the search from
+     * @param value The value to search for
+     * @return Optional containing the found node, or empty if not found
+     */
+    public Optional<Node<T>> search(final Node<T> root, final T value) {
+        if (root == null) {
             return Optional.empty();
         }
-        if (node.getValue().equals(value)) {
-            // add root node to visited
-            visited.add(value);
-            return Optional.of(node);
-        }
-        visited.add(node.getValue());
 
-        Queue<Node<T>> queue = new ArrayDeque<>(node.getChildren());
+        visited.add(root.getValue());
+        visitedSet.add(root.getValue());
+
+        if (root.getValue() == value) {
+            return Optional.of(root);
+        }
 
+        Queue<Node<T>> queue = new ArrayDeque<>(root.getChildren());
         while (!queue.isEmpty()) {
             final Node<T> current = queue.poll();
-            visited.add(current.getValue());
+            T currentValue = current.getValue();
+
+            if (visitedSet.contains(currentValue)) {
+                continue;
+            }
+
+            visited.add(currentValue);
+            visitedSet.add(currentValue);
 
-            if (current.getValue().equals(value)) {
+            if (currentValue == value || (value != null && value.equals(currentValue))) {
                 return Optional.of(current);
             }
 
@@ -43,6 +60,11 @@ public Optional<Node<T>> search(final Node<T> node, final T value) {
         return Optional.empty();
     }
 
+    /**
+     * Returns the list of nodes in the order they were visited.
+     *
+     * @return List containing the visited nodes
+     */
     public List<T> getVisited() {
         return visited;
     }

src/main/java/com/thealgorithms/sorts/AdaptiveMergeSort.java

@@ -0,0 +1,40 @@
+package com.thealgorithms.sorts;
+
+public class AdaptiveMergeSort implements SortAlgorithm {
+    @SuppressWarnings("unchecked")
+    public <T extends Comparable<T>> T[] sort(T[] array) {
+        if (array.length <= 1) {
+            return array;
+        }
+        T[] aux = array.clone();
+        sort(array, aux, 0, array.length - 1);
+        return array;
+    }
+
+    private <T extends Comparable<T>> void sort(T[] array, T[] aux, int low, int high) {
+        if (low >= high) {
+            return;
+        }
+        int mid = low + (high - low) / 2;
+        sort(array, aux, low, mid);
+        sort(array, aux, mid + 1, high);
+        merge(array, aux, low, mid, high);
+    }
+
+    private <T extends Comparable<T>> void merge(T[] array, T[] aux, int low, int mid, int high) {
+        System.arraycopy(array, low, aux, low, high - low + 1);
+        int i = low;
+        int j = mid + 1;
+        for (int k = low; k <= high; k++) {
+            if (i > mid) {
+                array[k] = aux[j++];
+            } else if (j > high) {
+                array[k] = aux[i++];
+            } else if (aux[j].compareTo(aux[i]) < 0) {
+                array[k] = aux[j++];
+            } else {
+                array[k] = aux[i++];
+            }
+        }
+    }
+}

src/main/java/com/thealgorithms/sorts/StalinSort.java

@@ -0,0 +1,21 @@
+package com.thealgorithms.sorts;
+
+public class StalinSort implements SortAlgorithm {
+    @SuppressWarnings("unchecked")
+    public <T extends Comparable<T>> T[] sort(T[] array) {
+        if (array.length == 0) {
+            return array;
+        }
+        int currentIndex = 0;
+        for (int i = 1; i < array.length; i++) {
+            if (array[i].compareTo(array[currentIndex]) >= 0) {
+                currentIndex++;
+                array[currentIndex] = array[i];
+            }
+        }
+        // Create a result array with sorted elements
+        T[] result = (T[]) java.lang.reflect.Array.newInstance(array.getClass().getComponentType(), currentIndex + 1);
+        System.arraycopy(array, 0, result, 0, currentIndex + 1);
+        return result;
+    }
+}

src/test/java/com/thealgorithms/dynamicprogramming/RodCuttingTest.java

@@ -93,4 +93,10 @@ void testCutRodEmptyPrices() {
         int length = 5;
         assertThrows(IllegalArgumentException.class, () -> RodCutting.cutRod(prices, length), "An empty prices array should throw an IllegalArgumentException.");
     }
+    @Test
+    void testCutRodNegativeLength() {
+        int[] prices = {1, 5, 8, 9, 10}; // Prices are irrelevant for negative length
+        int length = -1;
+        assertThrows(IllegalArgumentException.class, () -> RodCutting.cutRod(prices, length), "A negative rod length should throw an IllegalArgumentException.");
+    }
 }

src/test/java/com/thealgorithms/maths/GCDTest.java

@@ -40,6 +40,11 @@ void test7() {
         Assertions.assertEquals(GCD.gcd(9, 6), 3);
     }
 
+    @Test
+    void test8() {
+        Assertions.assertEquals(GCD.gcd(48, 18, 30, 12), 6);
+    }
+
     @Test
     void testArrayGcd1() {
         Assertions.assertEquals(GCD.gcd(new int[] {9, 6}), 3);

src/test/java/com/thealgorithms/maths/KrishnamurthyNumberTest.java

@@ -0,0 +1,62 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for the KrishnamurthyNumber class.
+ */
+public class KrishnamurthyNumberTest {
+
+    /**
+     * Test the isKrishnamurthy method with a known Krishnamurthy number.
+     */
+    @Test
+    public void testIsKrishnamurthyTrue() {
+        assertTrue(KrishnamurthyNumber.isKrishnamurthy(145));
+    }
+
+    /**
+     * Test the isKrishnamurthy method with a number that is not a Krishnamurthy number.
+     */
+    @Test
+    public void testIsKrishnamurthyFalse() {
+        assertFalse(KrishnamurthyNumber.isKrishnamurthy(123));
+    }
+
+    /**
+     * Test the isKrishnamurthy method with zero.
+     */
+    @Test
+    public void testIsKrishnamurthyZero() {
+        assertFalse(KrishnamurthyNumber.isKrishnamurthy(0));
+    }
+
+    /**
+     * Test the isKrishnamurthy method with a negative number.
+     */
+    @Test
+    public void testIsKrishnamurthyNegative() {
+        assertFalse(KrishnamurthyNumber.isKrishnamurthy(-145));
+    }
+
+    /**
+     * Test the isKrishnamurthy method with a single-digit Krishnamurthy number.
+     */
+    @Test
+    public void testIsKrishnamurthySingleDigitTrue() {
+        assertTrue(KrishnamurthyNumber.isKrishnamurthy(1));
+        assertTrue(KrishnamurthyNumber.isKrishnamurthy(2));
+    }
+
+    /**
+     * Test the isKrishnamurthy method with a single-digit number that is not a Krishnamurthy number.
+     */
+    @Test
+    public void testIsKrishnamurthySingleDigitFalse() {
+        assertFalse(KrishnamurthyNumber.isKrishnamurthy(3));
+        assertFalse(KrishnamurthyNumber.isKrishnamurthy(4));
+    }
+}