I have encountered to this question and applied a brute force algorithm off top of my head and couldn't find a better optimized solution.

I was hoping I could get some insight to implement a better optimized code in terms of complexity. My solution has O(N2) as well as O(n2) space.

class Solution:

def longestPalindrome(self, s: 'str') -> 'str':
    if s=="":
        return ""
    else:
       ## Find all the substrings
        arr=[]
        for i in range(len(s)):
            char = s[i]
            arr.append(char)
            for j in range(i+1, len(s)-1):
                char+=s[j]
                arr.append(char)

        ##Find the palindrome with a longest length
        max_length = 0
        for j in range(len(arr)):
            if self.isPalindrome(arr[j]):
                if len(arr[j]) > max_length:
                    max_length = len(arr[j])
                    index = arr[j]
        return index

    
def isPalindrome(self,s:'str')->'str':
    if s == s[::-1]:
        return True