Problem Solving

[Leetcode] 125. Valid Palindrome

leeyngdo 2023. 7. 12. 17:12

Problem Link: https://leetcode.com/problems/valid-palindrome/

 

Valid Palindrome - LeetCode

Can you solve this real interview question? Valid Palindrome - 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 cha

leetcode.com

 

Solution 1. Two Pointers

Time: $O(N)$

Space: $O(1)$ 

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