Day Day Code:125. Valid Palindrome有效回文串

125. Valid Palindrome

题目：A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.

Given a string s, return true if it is a palindrome, or false otherwise.

翻译一下：就是有效回文串

思路：
首先将字符串中数字、字母提取出来，并且将所有字母转换为小写，存入新列表。
然后利用双指针解决问题

话不多说上代码

class Solution(object):def isPalindrome(self, s):""":type s: str:rtype: bool"""list=[]#convert numbers and characters and put them in a listfor charc in s:if charc.isalnum():list.append(charc.lower())#convert list to strings="".join(list)#Two-pointersleft = 0right = len(s)-1while left