kazi1@的部落格

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.

class Solution(object):
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        left = 0
        right = len(s) - 1
        while left < right:
            while not s[left].isalnum() and left < len(s) - 1:
                left += 1
            while not s[right].isalnum() and right > 0:
                right -= 1
            if left < right and s[left].lower() != s[right].lower():
                return False
            else:
                left += 1
                right -= 1
        return True

PYTHONIC WAY!  用壓土機把它推下去...

class Solution(object):
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        s = re.sub('[^a-zA-Z0-9]+', '', s).lower()
        return s == s[::-1]