5. Longest Palindromic Substring Leetcode Python 2016 new Season

Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.

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There are two cases we need to deal with odd like 'ada' even like 'adda'

class Solution(object):
    def getPalindromeString(self, s, left_index, right_index):
        while left_index >= 0 and right_index < len(s) and s[left_index] == s[right_index]:
            left_index -= 1
            right_index += 1
        return s[left_index + 1 : right_index]
    def longestPalindrome(self, s):
        """
        :type s: str
        :rtype: str
        """
        longest_string = ''
        for  index in range(len(s)):
            first_string = self.getPalindromeString(s, index, index)
            second_string = self.getPalindromeString(s, index, index + 1)
            if len(first_string) > len(longest_string):
                longest_string = first_string
            if len(second_string) > len(longest_string):
                longest_string = second_string
        return longest_string