longest_palindromic_substring.py

class Solution:
    def longestPalindrome(self, s: str) -> str:
        start_longest = end_longest = 0
        for i in range(len(s)):
            for k in range(2):
                curr_start_longest, curr_end_longest = i, i + k
                while (curr_start_longest >= 0 and
                       curr_end_longest < len(s)
                       and s[curr_start_longest] == s[curr_end_longest]):
                    curr_start_longest -= 1
                    curr_end_longest += 1
                curr_start_longest += 1
                if curr_end_longest - curr_start_longest > end_longest - start_longest:
                    start_longest, end_longest = curr_start_longest, curr_end_longest
        return s[start_longest: end_longest]


sol = Solution()
assert sol.longestPalindrome("r") == "r"
assert sol.longestPalindrome("rars") == "rar"