[leetcode]Valid Palindrome @ Python

原题地址：https://oj.leetcode.com/problems/valid-palindrome/

题意：

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.

解题思路：将不是字母的字符去掉，然后转换成小写，然后简单的回文判断。

代码：

class Solution:
    # @param s, a string
    # @return a boolean
    def isPalindrome(self, s):
        if s == '':
            return True
        else:
            sTmp = ''
            for i in range(0, len(s)):
                if s[i] >= 'a' and s[i] <= 'z' or s[i] >= '0' and s[i] <= '9' or s[i] >= 'A' and s[i] <= 'Z':
                    sTmp += s[i]
            sTmp = sTmp.lower()
            for i in range(0, len(sTmp)/2):
                if sTmp[i] != sTmp[len(sTmp)-1-i]:
                    return False
            return True