python-leetcode-最长回文子串

5. 最长回文子串 - 力扣（LeetCode）

class Solution:
    def longestPalindrome(self, s: str) -> str:
        if not s:
            return ""

        def expandAroundCenter(left: int, right: int) -> str:
            while left >= 0 and right < len(s) and s[left] == s[right]:
                left -= 1
                right += 1
            return s[left+1:right]

        longest = ""
        for i in range(len(s)):
            # 奇数回文
            odd = expandAroundCenter(i, i)
            # 偶数回文
            even = expandAroundCenter(i, i+1)
            # 更新最长回文
            longest = max(longest, odd, even, key=len)

        return longest