From 5e1d89d8559421d1edb4ee0e87305febac15b2d3 Mon Sep 17 00:00:00 2001
From: alxkm <alx@alx.com>
Date: Mon, 26 Aug 2024 15:21:16 +0200
Subject: [PATCH 1/2] LongestPalindromicSubstring

---
 .../strings/LongestPalindromicSubstring.java  | 33 +++++++------------
 .../LongestPalindromicSubstringTest.java      | 21 ++++++++++++
 2 files changed, 32 insertions(+), 22 deletions(-)
 create mode 100644 src/test/java/com/thealgorithms/strings/LongestPalindromicSubstringTest.java

diff --git a/src/main/java/com/thealgorithms/strings/LongestPalindromicSubstring.java b/src/main/java/com/thealgorithms/strings/LongestPalindromicSubstring.java
index fa9171133a15..7106aacb2408 100644
--- a/src/main/java/com/thealgorithms/strings/LongestPalindromicSubstring.java
+++ b/src/main/java/com/thealgorithms/strings/LongestPalindromicSubstring.java
@@ -1,33 +1,22 @@
 package com.thealgorithms.strings;
 
-// Longest Palindromic Substring
-import java.util.Scanner;
-
 final class LongestPalindromicSubstring {
     private LongestPalindromicSubstring() {
     }
 
-    public static void main(String[] args) {
-        Solution s = new Solution();
-        String str = "";
-        Scanner sc = new Scanner(System.in);
-        System.out.print("Enter the string: ");
-        str = sc.nextLine();
-        System.out.println("Longest substring is : " + s.longestPalindrome(str));
-        sc.close();
-    }
-}
-
-class Solution {
-
-    public String longestPalindrome(String s) {
-        if (s == null || s.length() == 0) {
+    /**
+     * Finds the longest palindromic substring in the given string.
+     *
+     * @param s the input string
+     * @return the longest palindromic substring
+     */
+    public static String longestPalindrome(String s) {
+        if (s == null || s.isEmpty()) {
             return "";
         }
-        int n = s.length();
         String maxStr = "";
-        for (int i = 0; i < n; ++i) {
-            for (int j = i; j < n; ++j) {
+        for (int i = 0; i < s.length(); ++i) {
+            for (int j = i; j < s.length(); ++j) {
                 if (isValid(s, i, j)) {
                     if (j - i + 1 > maxStr.length()) { // update maxStr
                         maxStr = s.substring(i, j + 1);
@@ -38,7 +27,7 @@ public String longestPalindrome(String s) {
         return maxStr;
     }
 
-    private boolean isValid(String s, int lo, int hi) {
+    private static boolean isValid(String s, int lo, int hi) {
         int n = hi - lo + 1;
         for (int i = 0; i < n / 2; ++i) {
             if (s.charAt(lo + i) != s.charAt(hi - i)) {
diff --git a/src/test/java/com/thealgorithms/strings/LongestPalindromicSubstringTest.java b/src/test/java/com/thealgorithms/strings/LongestPalindromicSubstringTest.java
new file mode 100644
index 000000000000..aa13c0f4a474
--- /dev/null
+++ b/src/test/java/com/thealgorithms/strings/LongestPalindromicSubstringTest.java
@@ -0,0 +1,21 @@
+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;
+
+class LongestPalindromicSubstringTest {
+
+    @ParameterizedTest
+    @MethodSource("provideTestCasesForLongestPalindrome")
+    void testLongestPalindrome(String input, String expected) {
+        assertEquals(expected, LongestPalindromicSubstring.longestPalindrome(input));
+    }
+
+    private static Stream<Arguments> provideTestCasesForLongestPalindrome() {
+        return Stream.of(Arguments.of("babad", "bab"), Arguments.of("cbbd", "bb"), Arguments.of("a", "a"), Arguments.of("", ""), Arguments.of("abc", "a"), Arguments.of(null, ""), Arguments.of("aaaaa", "aaaaa"));
+    }
+}

From f9ca511c99ccf4501ddb9f061353ba83242e6498 Mon Sep 17 00:00:00 2001
From: alxkm <alx@alx.com>
Date: Mon, 26 Aug 2024 15:31:10 +0200
Subject: [PATCH 2/2] fix Rule:CollapsibleIfStatements

---
 .../thealgorithms/strings/LongestPalindromicSubstring.java  | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/main/java/com/thealgorithms/strings/LongestPalindromicSubstring.java b/src/main/java/com/thealgorithms/strings/LongestPalindromicSubstring.java
index 7106aacb2408..ca500357ba77 100644
--- a/src/main/java/com/thealgorithms/strings/LongestPalindromicSubstring.java
+++ b/src/main/java/com/thealgorithms/strings/LongestPalindromicSubstring.java
@@ -17,10 +17,8 @@ public static String longestPalindrome(String s) {
         String maxStr = "";
         for (int i = 0; i < s.length(); ++i) {
             for (int j = i; j < s.length(); ++j) {
-                if (isValid(s, i, j)) {
-                    if (j - i + 1 > maxStr.length()) { // update maxStr
-                        maxStr = s.substring(i, j + 1);
-                    }
+                if (isValid(s, i, j) && (j - i + 1 > maxStr.length())) {
+                    maxStr = s.substring(i, j + 1);
                 }
             }
         }