[LeetCode]题解（python）：125 Valid Palindrome

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