[Leetcode][python]Valid Palindrome/验证回文串

class Solution(object):
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        ss = []  # 这里若用string也可以，但是大数据会TLE
        for char in s.lower():
            if char.isalnum():
                ss.append(char)
        return ss == ss[::-1]

class Solution:
    # @param s, a string
    # @return a boolean
    def isPalindrome(self, s):
        if not s:
            return True

        s = s.lower()

        cl = 0
        cr = len(s)-1
        while cl <= cr:
            if not s[cl].isalnum():
                cl += 1
                continue

            if not s[cr].isalnum():
                cr -= 1
                continue

            if s[cl] != s[cr]:
                return False

            cl += 1
            cr -= 1

        return True