Merge branch 'master' into master

Author: jasonjyu

.github/workflows/build.yml

@@ -10,7 +10,7 @@ jobs:
         uses: actions/setup-java@v4
         with:
           java-version: 21
-          distribution: 'adopt'
+          distribution: 'temurin'
       - name: Build with Maven
         run: mvn --batch-mode --update-snapshots verify
       - name: Upload coverage to codecov (tokenless)

.github/workflows/codeql.yml

@@ -30,7 +30,7 @@ jobs:
         uses: actions/setup-java@v4
         with:
           java-version: 21
-          distribution: 'adopt'
+          distribution: 'temurin'
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v3

.github/workflows/infer.yml

@@ -18,7 +18,7 @@ jobs:
         uses: actions/setup-java@v4
         with:
           java-version: 21
-          distribution: 'adopt'
+          distribution: 'temurin'
 
       - name: Set up OCaml
         uses: ocaml/setup-ocaml@v3

DIRECTORY.md

@@ -183,7 +183,7 @@
     <!-- See https://checkstyle.org/checks/misc/index.html -->
     <module name="ArrayTypeStyle"/>
     <!-- TODO <module name="FinalParameters"/> -->
-    <!-- TODO <module name="TodoComment"/> -->
+    <module name="TodoComment"/>
     <module name="UpperEll"/>
 
     <!-- https://checkstyle.org/filters/suppressionxpathfilter.html -->

checkstyle.xml

@@ -40,6 +40,13 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <version>5.14.2</version>
+            <scope>test</scope>
+        </dependency>
+
 
         <dependency>
             <groupId>org.junit.jupiter</groupId>

pom.xml

@@ -87,9 +87,6 @@
         <Bug pattern="RCN_REDUNDANT_NULLCHECK_OF_NONNULL_VALUE" />
     </Match>
     <!-- fb-contrib -->
-    <Match>
-        <Bug pattern="OCP_OVERLY_CONCRETE_PARAMETER" />
-    </Match>
     <Match>
         <Bug pattern="LSC_LITERAL_STRING_COMPARISON" />
     </Match>

spotbugs-exclude.xml

@@ -4,32 +4,44 @@
 import java.util.List;
 
 /**
- * Finds all combinations of 0...n-1 of length k
+ * This class provides methods to find all combinations of integers from 0 to n-1
+ * of a specified length k using backtracking.
  */
 public final class ArrayCombination {
     private ArrayCombination() {
     }
 
     /**
-     * Finds all combinations of length k of 0..n-1 using backtracking.
+     * Generates all possible combinations of length k from the integers 0 to n-1.
      *
-     * @param n Number of the elements.
-     * @param k Length of the combination.
-     * @return A list of all combinations of length k.
+     * @param n The total number of elements (0 to n-1).
+     * @param k The desired length of each combination.
+     * @return A list containing all combinations of length k.
+     * @throws IllegalArgumentException if n or k are negative, or if k is greater than n.
      */
     public static List<List<Integer>> combination(int n, int k) {
         if (n < 0 || k < 0 || k > n) {
-            throw new IllegalArgumentException("Wrong input.");
+            throw new IllegalArgumentException("Invalid input: n must be non-negative, k must be non-negative and less than or equal to n.");
         }
 
         List<List<Integer>> combinations = new ArrayList<>();
         combine(combinations, new ArrayList<>(), 0, n, k);
         return combinations;
     }
 
+    /**
+     * A helper method that uses backtracking to find combinations.
+     *
+     * @param combinations The list to store all valid combinations found.
+     * @param current The current combination being built.
+     * @param start The starting index for the current recursion.
+     * @param n The total number of elements (0 to n-1).
+     * @param k The desired length of each combination.
+     */
     private static void combine(List<List<Integer>> combinations, List<Integer> current, int start, int n, int k) {
-        if (current.size() == k) { // Base case: combination found
-            combinations.add(new ArrayList<>(current)); // Copy to avoid modification
+        // Base case: combination found
+        if (current.size() == k) {
+            combinations.add(new ArrayList<>(current));
             return;
         }
 

src/main/java/com/thealgorithms/backtracking/ArrayCombination.java

@@ -1,6 +1,7 @@
 package com.thealgorithms.backtracking;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 
 /**
@@ -95,7 +96,7 @@ public static void removeWord(char[][] puzzle, String word, int row, int col, bo
      * @param words  The list of words to be placed.
      * @return true if the crossword is solved, false otherwise.
      */
-    public static boolean solveCrossword(char[][] puzzle, List<String> words) {
+    public static boolean solveCrossword(char[][] puzzle, Collection<String> words) {
         // Create a mutable copy of the words list
         List<String> remainingWords = new ArrayList<>(words);
 

src/main/java/com/thealgorithms/backtracking/CrosswordSolver.java

@@ -0,0 +1,82 @@
+package com.thealgorithms.bitmanipulation;
+
+/**
+ * This class provides methods to convert between BCD (Binary-Coded Decimal) and decimal numbers.
+ *
+ * BCD is a class of binary encodings of decimal numbers where each decimal digit is represented by a fixed number of binary digits, usually four or eight.
+ *
+ * For more information, refer to the
+ * <a href="https://en.wikipedia.org/wiki/Binary-coded_decimal">Binary-Coded Decimal</a> Wikipedia page.
+ *
+ * <b>Example usage:</b>
+ * <pre>
+ * int decimal = BcdConversion.bcdToDecimal(0x1234);
+ * System.out.println("BCD 0x1234 to decimal: " + decimal); // Output: 1234
+ *
+ * int bcd = BcdConversion.decimalToBcd(1234);
+ * System.out.println("Decimal 1234 to BCD: " + Integer.toHexString(bcd)); // Output: 0x1234
+ * </pre>
+ */
+public final class BcdConversion {
+    private BcdConversion() {
+    }
+
+    /**
+     * Converts a BCD (Binary-Coded Decimal) number to a decimal number.
+     * <p>Steps:
+     * <p>1. Validate the BCD number to ensure all digits are between 0 and 9.
+     * <p>2. Extract the last 4 bits (one BCD digit) from the BCD number.
+     * <p>3. Multiply the extracted digit by the corresponding power of 10 and add it to the decimal number.
+     * <p>4. Shift the BCD number right by 4 bits to process the next BCD digit.
+     * <p>5. Repeat steps 1-4 until the BCD number is zero.
+     *
+     * @param bcd The BCD number.
+     * @return The corresponding decimal number.
+     * @throws IllegalArgumentException if the BCD number contains invalid digits.
+     */
+    public static int bcdToDecimal(int bcd) {
+        int decimal = 0;
+        int multiplier = 1;
+
+        // Validate BCD digits
+        while (bcd > 0) {
+            int digit = bcd & 0xF;
+            if (digit > 9) {
+                throw new IllegalArgumentException("Invalid BCD digit: " + digit);
+            }
+            decimal += digit * multiplier;
+            multiplier *= 10;
+            bcd >>= 4;
+        }
+        return decimal;
+    }
+
+    /**
+     * Converts a decimal number to BCD (Binary-Coded Decimal).
+     * <p>Steps:
+     * <p>1. Check if the decimal number is within the valid range for BCD (0 to 9999).
+     * <p>2. Extract the last decimal digit from the decimal number.
+     * <p>3. Shift the digit to the correct BCD position and add it to the BCD number.
+     * <p>4. Remove the last decimal digit from the decimal number.
+     * <p>5. Repeat steps 2-4 until the decimal number is zero.
+     *
+     * @param decimal The decimal number.
+     * @return The corresponding BCD number.
+     * @throws IllegalArgumentException if the decimal number is greater than 9999.
+     */
+    public static int decimalToBcd(int decimal) {
+        if (decimal < 0 || decimal > 9999) {
+            throw new IllegalArgumentException("Value out of bounds for BCD representation: " + decimal);
+        }
+
+        int bcd = 0;
+        int shift = 0;
+        while (decimal > 0) {
+            int digit = decimal % 10;
+            bcd |= (digit << (shift * 4));
+            decimal /= 10;
+            shift++;
+        }
+        return bcd;
+    }
+}