[Python手撕]最长回文子串

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

        n = len(s)

        def find(i, j):
            if i != j and s[i] != s[j]:
                return 0,-1

            while (
                0 <= i <= n -1
                and 0 <= j <= n -1
                and s[i] == s[j]
                and 0 <= i - 1 <= n -1
                and 0 <= j + 1 <= n -1
                and s[i - 1] == s[j + 1]
            ):
                i -= 1
                j += 1
            return i,j

        index = 0
        max_len = 1
        res = s[0]
        while index<=n-1:
            left = floor(index)
            right = ceil(index)
            left,right = find(left,right)
            if right - left + 1 > max_len:
                res = s[left:right+1]
                max_len = right - left + 1
            index += 0.5
        
        return res