5.最长回文子串

class Solution:
    def longestPalindrome(self, s: str) -> str:
        best_str =''
        cnt_best_str =0 
        for i in range(len(s)):
            # aba 
            left ,right =i,i 
            cur_string=''
            cur_cnt =0
            while left >=0 and right< len(s) and s[left] == s[right]:
               
                left -=1
                right +=1
                
            cur_string=s[left+1:right]
            cur_cnt =right-left-1
            if cur_cnt >cnt_best_str:
                best_str =cur_string
                cnt_best_str = cur_cnt
            
            #abba 
            left =i 
            right= i+1
            while left >=0 and right< len(s) and s[left] == s[right]:
                
                left -=1
                right +=1
            cur_string=s[left+1:right]
            cur_cnt =right-left-1
            if cur_cnt >cnt_best_str:
                best_str =cur_string
                cnt_best_str = cur_cnt
        return best_str