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.