Problem Statement
Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
Note: For the purpose of this problem, we define empty string as valid palindrome.
Example 1:
Input: "A man, a plan, a canal: Panama" Output: true
Example 2:
Input: "race a car" Output: false
Solution:
class Solution:
def isPalindrome(self, s: str) -> bool:
if not s:
return True
s = s.lower()
i=0
j = len(s)-1
while i<j:
while not s[i].isalnum() and i<j:
i+=1
while not s[j].isalnum() and i<j:
j-=1
if s[i]!=s[j]:
return False
i+=1
j-=1
return True
