题目来源

https://leetcode.com/problems/valid-palindrome/

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

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

Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.

For the purpose of this problem, we define empty string as valid palindrome.

题意分析

Input: a string

Output: whether the string is valid palindrome

Conditions: 判断是否是回文串，忽略非数字和非字母的字符

题目思路

采用isalnum来判断是否为字母或数字，然后将字符转为小写（题目认为大小写是一样的），然后简单判断是否是回文。

AC代码（Python）

 class Solution(object):

     def isPalindrome(self, s):

         """

         :type s: str

         :rtype: bool

         """

         c = []

         for i in s:

             if i.isalnum():

                 c.append(i.lower())

         for i in range(len(c)/2):

             if c[i] != c[len(c)-1-i]:

                 return False

         return True