Add Manacher’s Algorithm for Longest Palindromic Substring (#5462)

* Added Manacher Algorithm

* Formatted ManacherTest.java

* Formatted Manacher.java

* Refactor: Update Manacher's algorithm tests and improve readability

- Added parameterized tests for longestPalindrome, empty cases, complex cases, and sentence palindromes.
- Removed unnecessary comments for cleaner code.
- Renamed variable `p` to `palindromeLengths` for clarity based on code review feedback.

---------

Co-authored-by: Ionut Hodoroaga <ionut.hodoroaga20@gmail.com>

src/test/java/com/thealgorithms/strings/ManacherTest.java

@@ -0,0 +1,53 @@
+package com.thealgorithms.strings;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+public class ManacherTest {
+
+    @ParameterizedTest
+    @MethodSource("provideTestCasesForLongestPalindrome")
+    public void testLongestPalindrome(String input, String expected) {
+        assertEquals(expected, Manacher.longestPalindrome(input));
+    }
+
+    private static Stream<Arguments> provideTestCasesForLongestPalindrome() {
+        return Stream.of(Arguments.of("abracadabraabcdefggfedcbaabracadabra", "aabcdefggfedcbaa"), Arguments.of("somelongtextwithracecarmiddletext", "racecar"), Arguments.of("bananananananana", "ananananananana"), Arguments.of("qwertydefgfedzxcvbnm", "defgfed"),
+            Arguments.of("abcdefghijklmnopqrstuvwxyzzyxwvutsrqponmlkjihgfedcba", "abcdefghijklmnopqrstuvwxyzzyxwvutsrqponmlkjihgfedcba"));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestCasesForEmptyAndSingle")
+    public void testEmptyAndSingle(String input, String expected) {
+        assertEquals(expected, Manacher.longestPalindrome(input));
+    }
+
+    private static Stream<Arguments> provideTestCasesForEmptyAndSingle() {
+        return Stream.of(Arguments.of("", ""), Arguments.of("a", "a"));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestCasesForComplexCases")
+    public void testComplexCases(String input, String expected) {
+        assertEquals(expected, Manacher.longestPalindrome(input));
+    }
+
+    private static Stream<Arguments> provideTestCasesForComplexCases() {
+        return Stream.of(Arguments.of("abcdefghijklmnopqrstuvwxyzttattarrattatabcdefghijklmnopqrstuvwxyz", "tattarrattat"), Arguments.of("aaaaabaaaaacbaaaaa", "aaaaabaaaaa"), Arguments.of("sometextrandomabcdefgabcdefghhgfedcbahijklmnopqrstuvwxyz", "abcdefghhgfedcba"),
+            Arguments.of("therewasasignthatsaidmadaminedenimadamitwasthereallalong", "madaminedenimadam"));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestCasesForSentencePalindromes")
+    public void testSentencePalindromes(String input, String expected) {
+        assertEquals(expected, Manacher.longestPalindrome(input));
+    }
+
+    private static Stream<Arguments> provideTestCasesForSentencePalindromes() {
+        return Stream.of(Arguments.of("XThisisalongtextbuthiddeninsideisAmanaplanacanalPanamaWhichweknowisfamous", "lanacanal"), Arguments.of("AverylongstringthatcontainsNeveroddoreveninahiddenmanner", "everoddoreve"));
+    }
+}