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/test/java/com/thealgorithms/compression/RunLengthEncodingTest.java

@@ -0,0 +1,90 @@
+package com.thealgorithms.compression;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class RunLengthEncodingTest {
+
+    @Test
+    void testNullInputs() {
+        // Test that a null input to compress returns an empty string
+        assertEquals("", RunLengthEncoding.compress(null));
+
+        // Test that a null input to decompress returns an empty string
+        assertEquals("", RunLengthEncoding.decompress(null));
+    }
+
+    @Test
+    void testCompressionSimple() {
+        // Test a typical string with multiple runs
+        String input = "AAAABBBCCDAA";
+        String expected = "4A3B2C1D2A";
+        assertEquals(expected, RunLengthEncoding.compress(input));
+    }
+
+    @Test
+    void testCompressionWithNoRuns() {
+        // Test a string with no consecutive characters
+        String input = "ABCDE";
+        String expected = "1A1B1C1D1E";
+        assertEquals(expected, RunLengthEncoding.compress(input));
+    }
+
+    @Test
+    void testCompressionEdgeCases() {
+        // Test with an empty string
+        assertEquals("", RunLengthEncoding.compress(""));
+
+        // Test with a single character
+        assertEquals("1A", RunLengthEncoding.compress("A"));
+
+        // Test with a long run of a single character
+        assertEquals("10Z", RunLengthEncoding.compress("ZZZZZZZZZZ"));
+    }
+
+    @Test
+    void testDecompressionSimple() {
+        // Test decompression of a typical RLE string
+        String input = "4A3B2C1D2A";
+        String expected = "AAAABBBCCDAA";
+        assertEquals(expected, RunLengthEncoding.decompress(input));
+    }
+
+    @Test
+    void testDecompressionWithNoRuns() {
+        // Test decompression of a string with single characters
+        String input = "1A1B1C1D1E";
+        String expected = "ABCDE";
+        assertEquals(expected, RunLengthEncoding.decompress(input));
+    }
+
+    @Test
+    void testDecompressionWithMultiDigitCount() {
+        // Test decompression where a run count is greater than 9
+        String input = "12A1B3C";
+        String expected = "AAAAAAAAAAAABCCC";
+        assertEquals(expected, RunLengthEncoding.decompress(input));
+    }
+
+    @Test
+    void testDecompressionEdgeCases() {
+        // Test with an empty string
+        assertEquals("", RunLengthEncoding.decompress(""));
+
+        // Test with a single character run
+        assertEquals("A", RunLengthEncoding.decompress("1A"));
+    }
+
+    @Test
+    void testSymmetry() {
+        // Test that compressing and then decompressing returns the original string
+        String original1 = "WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWB";
+        String compressed = RunLengthEncoding.compress(original1);
+        String decompressed = RunLengthEncoding.decompress(compressed);
+        assertEquals(original1, decompressed);
+
+        String original2 = "A";
+        assertEquals(original2, RunLengthEncoding.decompress(RunLengthEncoding.compress(original2)));
+    }
+}