Leetcode 125: Valid Palindrome

125. Valid Palindrome 

  • Total Accepted: 124387
  • Total Submissions: 499823
  • Difficulty: Easy
  • Contributors: Admin

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.

 

Code

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

 

Idea

Not much to say. First time to use string.isalnum().

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