125.验证回文字符串leetcode

class Solution:
    def isPalindrome(self, s: str) -> bool:
       str_new=''.join([c.lower() for c in s if c.isalnum()]) 
       return str_new ==str_new[::-1]

class Solution:
    def isPalindrome(self, s: str) -> bool:
        left =0
        right =len(s)-1 
        s=s.lower()
        while left <right :
            while left<right and  not s[left].isalnum():
                left +=1
            while left<right and  not s[right].isalnum():
                right -=1
            if s[left] != s[right] : 
                return False 
            left +=1
            right -= 1
        return True