refactor: LongestPalindromicSubstring (#5420)

* refactor: LongestPalindromicSubstring

* checkstyle: fix formatting

---------

Co-authored-by: alxkm <alx@alx.com>

src/test/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstringTest.java

@@ -0,0 +1,22 @@
+package com.thealgorithms.dynamicprogramming;
+
+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 LongestPalindromicSubstringTest {
+
+    private static Stream<Arguments> provideTestCases() {
+        return Stream.of(
+            Arguments.of("babad", "aba"), Arguments.of("cbbd", "bb"), Arguments.of("a", "a"), Arguments.of("x", "x"), Arguments.of("", ""), Arguments.of("aaaa", "aaaa"), Arguments.of("mm", "mm"), Arguments.of("level", "level"), Arguments.of("bananas", "anana"), Arguments.of("abacabad", "abacaba"));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestCases")
+    public void testLps(String input, String expected) {
+        assertEquals(expected, LongestPalindromicSubstring.lps(input));
+    }
+}