From c413f3c6b2d031c1eb0e015d606d4cfd09e2be8f Mon Sep 17 00:00:00 2001
From: Alex Klymenko <alexanderklmn@gmail.com>
Date: Wed, 28 Aug 2024 18:35:21 +0200
Subject: [PATCH] refactor: `LongestPalindromicSubstring` (#5420)

* refactor: LongestPalindromicSubstring

* checkstyle: fix formatting

---------

Co-authored-by: alxkm <alx@alx.com>
---
 .../LongestPalindromicSubstring.java          | 23 +++++++------------
 .../LongestPalindromicSubstringTest.java      | 22 ++++++++++++++++++
 2 files changed, 30 insertions(+), 15 deletions(-)
 create mode 100644 src/test/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstringTest.java

diff --git a/src/main/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstring.java b/src/main/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstring.java
index c6ae55919..8a4ab2f52 100644
--- a/src/main/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstring.java
+++ b/src/main/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstring.java
@@ -1,25 +1,18 @@
 package com.thealgorithms.dynamicprogramming;
 
-/*
- * Algorithm explanation https://leetcode.com/problems/longest-palindromic-substring/
+/**
+ * Class for finding the longest palindromic substring within a given string.
+ * <p>
+ * A palindromic substring is a sequence of characters that reads the same backward as forward.
+ * This class uses a dynamic programming approach to efficiently find the longest palindromic substring.
+ *
  */
 public final class LongestPalindromicSubstring {
     private LongestPalindromicSubstring() {
     }
 
-    public static void main(String[] args) {
-        String a = "babad";
-        String b = "cbbd";
-
-        String aLPS = lps(a);
-        String bLPS = lps(b);
-
-        System.out.println(a + " => " + aLPS);
-        System.out.println(b + " => " + bLPS);
-    }
-
-    private static String lps(String input) {
-        if (input == null || input.length() == 0) {
+    public static String lps(String input) {
+        if (input == null || input.isEmpty()) {
             return input;
         }
         boolean[][] arr = new boolean[input.length()][input.length()];
diff --git a/src/test/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstringTest.java b/src/test/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstringTest.java
new file mode 100644
index 000000000..278de7e10
--- /dev/null
+++ b/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));
+    }
+}