# 5. Longest Palindromic Substring

https://leetcode.com/problems/longest-palindromic-substring/

Given a string s, return the longest palindromic substring in s.

```
Example 1:

Input: s = "babad"
Output: "bab"
Explanation: "aba" is also a valid answer.
Example 2:

Input: s = "cbbd"
Output: "bb"
 

Constraints:

1 <= s.length <= 1000
s consist of only digits and English letters.
```