Merge branch 'master' into feat/self-organizing-list

Author: iamcodinghere22

.github/dependabot.yml

@@ -5,14 +5,20 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+    cooldown:
+      default-days: 7
 
   - package-ecosystem: "github-actions"
     directory: "/.github/workflows/"
     schedule:
       interval: "daily"
+    cooldown:
+      default-days: 7
 
   - package-ecosystem: "maven"
     directory: "/"
     schedule:
       interval: "daily"
+    cooldown:
+      default-days: 7
 ...

.github/workflows/build.yml

@@ -10,7 +10,7 @@ jobs:
     steps:
       - uses: actions/checkout@v7
       - name: Set up JDK
-        uses: actions/setup-java@v5
+        uses: actions/setup-java@v5.7.0
         with:
           java-version: 21
           distribution: 'temurin'

.github/workflows/codeql.yml

@@ -24,21 +24,21 @@ jobs:
         uses: actions/checkout@v7
 
       - name: Set up JDK
-        uses: actions/setup-java@v5
+        uses: actions/setup-java@v5.7.0
         with:
           java-version: 21
           distribution: 'temurin'
 
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@v4
+        uses: github/codeql-action/init@v4.37.6
         with:
           languages: 'java-kotlin'
 
       - name: Build
         run: mvn --batch-mode --update-snapshots verify
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@v4
+        uses: github/codeql-action/analyze@v4.37.6
         with:
           category: "/language:java-kotlin"
 
@@ -55,12 +55,12 @@ jobs:
         uses: actions/checkout@v7
 
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@v4
+        uses: github/codeql-action/init@v4.37.6
         with:
           languages: 'actions'
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@v4
+        uses: github/codeql-action/analyze@v4.37.6
         with:
           category: "/language:actions"
 ...

.github/workflows/infer.yml

@@ -18,7 +18,7 @@ jobs:
       - uses: actions/checkout@v7
 
       - name: Set up JDK
-        uses: actions/setup-java@v5
+        uses: actions/setup-java@v5.7.0
         with:
           java-version: 21
           distribution: 'temurin'

.github/workflows/project_structure.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v7
-      - uses: actions/setup-python@v6
+      - uses: actions/setup-python@v7.0.0
         with:
           python-version: '3.13'
 

.github/workflows/stale.yml

@@ -11,7 +11,7 @@ jobs:
       pull-requests: write
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@v10
+      - uses: actions/stale@v11.0.0
         with:
           stale-issue-message: 'This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contribution!'
           close-issue-message: 'Please reopen this issue once you have made the required changes. If you need help, feel free to ask in our [Discord](https://the-algorithms.com/discord) server or ping one of the maintainers here. Thank you for your contribution!'

pom.xml

@@ -20,7 +20,7 @@
             <dependency>
                 <groupId>org.junit</groupId>
                 <artifactId>junit-bom</artifactId>
-                <version>6.1.0</version>
+                <version>6.1.3</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -53,7 +53,7 @@
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-collections4</artifactId>
-            <version>4.5.0</version>
+            <version>4.6.0</version>
         </dependency>
     </dependencies>
 
@@ -112,14 +112,14 @@
                     <dependency>
                     <groupId>com.puppycrawl.tools</groupId>
                     <artifactId>checkstyle</artifactId>
-                    <version>13.6.0</version>
+                    <version>13.10.0</version>
                     </dependency>
                 </dependencies>
             </plugin>
             <plugin>
                 <groupId>com.github.spotbugs</groupId>
                 <artifactId>spotbugs-maven-plugin</artifactId>
-                <version>4.10.2.0</version>
+                <version>4.10.3.0</version>
                 <configuration>
                     <excludeFilterFile>spotbugs-exclude.xml</excludeFilterFile>
                     <includeTests>true</includeTests>

spotbugs-exclude.xml

@@ -59,6 +59,12 @@
     <Match>
         <Bug pattern="AT_STALE_THREAD_WRITE_OF_PRIMITIVE" />
     </Match>
+    <Match>
+        <Bug pattern="NP_NULL_PARAM_DEREF_NONVIRTUAL" />
+    </Match>
+    <Match>
+        <Bug pattern="NP_NULL_PARAM_DEREF_ALL_TARGETS_DANGEROUS" />
+    </Match>
     <!-- fb-contrib -->
     <Match>
         <Bug pattern="LSC_LITERAL_STRING_COMPARISON" />

src/main/java/com/thealgorithms/ciphers/Caesar.java

@@ -9,8 +9,8 @@
  * @author khalil2535
  */
 public class Caesar {
-    private static char normalizeShift(final int shift) {
-        return (char) (shift % 26);
+    private static int normalizeShift(final int shift) {
+        return ((shift % 26) + 26) % 26;
     }
 
     /**
@@ -22,21 +22,18 @@ private static char normalizeShift(final int shift) {
     public String encode(String message, int shift) {
         StringBuilder encoded = new StringBuilder();
 
-        final char shiftChar = normalizeShift(shift);
+        final int shiftChar = normalizeShift(shift);
 
         final int length = message.length();
         for (int i = 0; i < length; i++) {
-            //            int current = message.charAt(i); //using char to shift characters because
-            //            ascii
-            // is in-order latin alphabet
-            char current = message.charAt(i); // Java law : char + int = char
+            final char current = message.charAt(i);
 
             if (isCapitalLatinLetter(current)) {
-                current += shiftChar;
-                encoded.append((char) (current > 'Z' ? current - 26 : current)); // 26 = number of latin letters
+                final int shifted = current + shiftChar;
+                encoded.append((char) (shifted > 'Z' ? shifted - 26 : shifted)); // 26 = number of latin letters
             } else if (isSmallLatinLetter(current)) {
-                current += shiftChar;
-                encoded.append((char) (current > 'z' ? current - 26 : current)); // 26 = number of latin letters
+                final int shifted = current + shiftChar;
+                encoded.append((char) (shifted > 'z' ? shifted - 26 : shifted)); // 26 = number of latin letters
             } else {
                 encoded.append(current);
             }
@@ -53,17 +50,17 @@ public String encode(String message, int shift) {
     public String decode(String encryptedMessage, int shift) {
         StringBuilder decoded = new StringBuilder();
 
-        final char shiftChar = normalizeShift(shift);
+        final int shiftChar = normalizeShift(shift);
 
         final int length = encryptedMessage.length();
         for (int i = 0; i < length; i++) {
-            char current = encryptedMessage.charAt(i);
+            final char current = encryptedMessage.charAt(i);
             if (isCapitalLatinLetter(current)) {
-                current -= shiftChar;
-                decoded.append((char) (current < 'A' ? current + 26 : current)); // 26 = number of latin letters
+                final int shifted = current - shiftChar;
+                decoded.append((char) (shifted < 'A' ? shifted + 26 : shifted)); // 26 = number of latin letters
             } else if (isSmallLatinLetter(current)) {
-                current -= shiftChar;
-                decoded.append((char) (current < 'a' ? current + 26 : current)); // 26 = number of latin letters
+                final int shifted = current - shiftChar;
+                decoded.append((char) (shifted < 'a' ? shifted + 26 : shifted)); // 26 = number of latin letters
             } else {
                 decoded.append(current);
             }

src/main/java/com/thealgorithms/ciphers/RailFenceCipher.java

@@ -1,7 +1,5 @@
 package com.thealgorithms.ciphers;
 
-import java.util.Arrays;
-
 /**
  * The rail fence cipher (also called a zigzag cipher) is a classical type of transposition cipher.
  * It derives its name from the manner in which encryption is performed, in analogy to a fence built with horizontal rails.
@@ -14,28 +12,27 @@ public class RailFenceCipher {
     // Encrypts the input string using the rail fence cipher method with the given number of rails.
     public String encrypt(String str, int rails) {
 
+        checkInput(str, rails);
+
         // Base case of single rail or rails are more than the number of characters in the string
         if (rails == 1 || rails >= str.length()) {
             return str;
         }
 
-        // Boolean flag to determine if the movement is downward or upward in the rail matrix.
+        // Boolean flag to determine if the movement is downward or upward in the rail pattern.
         boolean down = true;
-        // Create a 2D array to represent the rails (rows) and the length of the string (columns).
-        char[][] strRail = new char[rails][str.length()];
-
-        // Initialize all positions in the rail matrix with a placeholder character ('\n').
+        // Collect the characters of every rail separately. Using one buffer per rail (instead of a
+        // rails x length matrix with a placeholder character) keeps every character of the input,
+        // including characters that would otherwise be indistinguishable from the placeholder.
+        StringBuilder[] railBuffers = new StringBuilder[rails];
         for (int i = 0; i < rails; i++) {
-            Arrays.fill(strRail[i], '\n');
+            railBuffers[i] = new StringBuilder();
         }
 
-        int row = 0; // Start at the first row
-        int col = 0; // Start at the first column
+        int row = 0; // Start at the first rail
 
-        int i = 0;
-
-        // Fill the rail matrix with characters from the string based on the rail pattern.
-        while (col < str.length()) {
+        // Distribute the characters of the string over the rails following the zigzag pattern.
+        for (int i = 0; i < str.length(); i++) {
             // Change direction to down when at the first row.
             if (row == 0) {
                 down = true;
@@ -45,33 +42,28 @@ else if (row == rails - 1) {
                 down = false;
             }
 
-            // Place the character in the current position of the rail matrix.
-            strRail[row][col] = str.charAt(i);
-            col++; // Move to the next column.
+            // Append the character to the rail it belongs to.
+            railBuffers[row].append(str.charAt(i));
             // Move to the next row based on the direction.
             if (down) {
                 row++;
             } else {
                 row--;
             }
-
-            i++;
         }
 
-        // Construct the encrypted string by reading characters row by row.
-        StringBuilder encryptedString = new StringBuilder();
-        for (char[] chRow : strRail) {
-            for (char ch : chRow) {
-                if (ch != '\n') {
-                    encryptedString.append(ch);
-                }
-            }
+        // Construct the encrypted string by reading the rails top to bottom.
+        StringBuilder encryptedString = new StringBuilder(str.length());
+        for (StringBuilder railBuffer : railBuffers) {
+            encryptedString.append(railBuffer);
         }
         return encryptedString.toString();
     }
     // Decrypts the input string using the rail fence cipher method with the given number of rails.
     public String decrypt(String str, int rails) {
 
+        checkInput(str, rails);
+
         // Base case of single rail or rails are more than the number of characters in the string
         if (rails == 1 || rails >= str.length()) {
             return str;
@@ -144,4 +136,14 @@ else if (row == rails - 1) {
 
         return decryptedString.toString();
     }
+
+    // Rejects inputs the zigzag pattern is not defined for.
+    private static void checkInput(String str, int rails) {
+        if (str == null) {
+            throw new IllegalArgumentException("Input string must not be null");
+        }
+        if (rails <= 0) {
+            throw new IllegalArgumentException("Number of rails must be positive, but was " + rails);
+        }
+    }
 }