5. Longest Palindromic Substring

Medium

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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.