> For the complete documentation index, see [llms.txt](https://luj.gitbook.io/code/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://luj.gitbook.io/code/string/6-palindrome/longest-palindromic-substring.md).

# Find Longest Palindromic Substring

Find the Longest Palindromic Substring for a string. Return "" if there is not one.

## Example

s = "abcccccc" return "cccccc"

## Note

首尾双指针 - O(n\*n)

## Code

```java
public String longestPalindrome(String s) {
   char[] chars = s.toCharArray();
   int len = s.length();
   while (len >= 0) {
       for (int i = 0; i + len - 1 < chars.length; i++) {
           int left = i;
           int right = i + len - 1;
           boolean good = true;
           while (left < right) {
               if (chars[left] != chars[right]) {
                   good = false;
                   break;
               }
               left++;
               right--;
           }
           if (good)
               return s.substring(i, i + len);
       }
       --len;
   }
   return "";
}
```