#5. Longest Palindromic Substring (even/odd ptrs)

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.

class Solution:

    def longestPalindrome(self, s: str) -> str:

       

        def expand(left,right):

            while left >= 0 and right < len(s) and s[left] == s[right]:

                left-=1

                right+=1

            print(left,right, s[left+1:right])

            return s[left+1:right]

   

        longest = ""

        for i in range(len(s)):

            odd = expand(i,i)

            if len(odd) > len(longest):

                longest = odd

            even  = expand(i,i+1)

            if len(even) > len(longest):

                longest = even

        return longest