feat: Add RLE and Shannon-Fano compression algorithms (#6779)

* feat: Add RLE and Shannon-Fano compression algorithms

* Fix: Resolve CI failures for compression algorithms

* chore: trigger CI rebuild

src/main/java/com/thealgorithms/compression/RunLengthEncoding.java

@@ -0,0 +1,87 @@
+package com.thealgorithms.compression;
+
+/**
+ * An implementation of the Run-Length Encoding (RLE) algorithm.
+ *
+ * <p>Run-Length Encoding is a simple form of lossless data compression in which
+ * runs of data (sequences in which the same data value occurs in many
+ * consecutive data elements) are stored as a single data value and count,
+ * rather than as the original run.
+ *
+ * <p>This implementation provides methods for both compressing and decompressing
+ * a string. For example:
+ * <ul>
+ * <li>Compressing "AAAABBBCCDAA" results in "4A3B2C1D2A".</li>
+ * <li>Decompressing "4A3B2C1D2A" results in "AAAABBBCCDAA".</li>
+ * </ul>
+ *
+ * <p>Time Complexity: O(n) for both compression and decompression, where n is the
+ * length of the input string.
+ *
+ * <p>References:
+ * <ul>
+ * <li><a href="https://en.wikipedia.org/wiki/Run-length_encoding">Wikipedia: Run-length encoding</a></li>
+ * </ul>
+ */
+public final class RunLengthEncoding {
+
+    /**
+     * Private constructor to prevent instantiation of this utility class.
+     */
+    private RunLengthEncoding() {
+    }
+
+    /**
+     * Compresses a string using the Run-Length Encoding algorithm.
+     *
+     * @param text The string to be compressed. Must not be null.
+     * @return The compressed string. Returns an empty string if the input is empty.
+     */
+    public static String compress(String text) {
+        if (text == null || text.isEmpty()) {
+            return "";
+        }
+
+        StringBuilder compressed = new StringBuilder();
+        int count = 1;
+
+        for (int i = 0; i < text.length(); i++) {
+            // Check if it's the last character or if the next character is different
+            if (i == text.length() - 1 || text.charAt(i) != text.charAt(i + 1)) {
+                compressed.append(count);
+                compressed.append(text.charAt(i));
+                count = 1; // Reset count for the new character
+            } else {
+                count++;
+            }
+        }
+        return compressed.toString();
+    }
+
+    /**
+     * Decompresses a string that was compressed using the Run-Length Encoding algorithm.
+     *
+     * @param compressedText The compressed string. Must not be null.
+     * @return The original, uncompressed string.
+     */
+    public static String decompress(String compressedText) {
+        if (compressedText == null || compressedText.isEmpty()) {
+            return "";
+        }
+
+        StringBuilder decompressed = new StringBuilder();
+        int count = 0;
+
+        for (char ch : compressedText.toCharArray()) {
+            if (Character.isDigit(ch)) {
+                // Build the number for runs of 10 or more (e.g., "12A")
+                count = count * 10 + ch - '0';
+            } else {
+                // Append the character 'count' times
+                decompressed.append(String.valueOf(ch).repeat(Math.max(0, count)));
+                count = 0; // Reset count for the next sequence
+            }
+        }
+        return decompressed.toString();
+    }
+}