leetcode:Valid Palindrome【Python版】

1、注意空字符串的处理；

2、注意是alphanumeric字符；

3、字符串添加字符直接用+就可以；

 class Solution:
     # @param s, a string
     # @return a boolean
     def isPalindrome(self, s):
         ret = False
         s = s.lower()
         ss = ""
         for i in s:
             if i.isalnum():
                 ss += i
         h = 0
         e = len(ss)-1
         while(h<e):
             if(ss[h] == ss[e]):
                 h += 1
                 e -= 1
             else:
                 break
         if h>=e:
             ret = True
         return ret