125. Valid Palindrome

Given a string, determine if it is a palindrome（回文）, considering only alphanumeric（字母数字的） characters and ignoring cases.

For example,
"A man, a plan, a canal: Panama" is a palindrome.
"race a car" is not a palindrome.

 

class Solution(object):
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        s = "".join([c.lower() for c in s if c.isalnum()])
        return s == s[::-1]     

c.lower()将字符串c中的大写字母转换成小写

c.isalnum()判断是否是字母或数字，若是返回非零