Valid Palindrome

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

Solution

class Solution:
    def isPalindrome(self, s: str) -> bool:
        l, r = 0, len(s)-1
        while l < r:
            if not s[l].isalnum():
                l += 1
            elif not s[r].isalnum():
                r -= 1
            elif s[l].lower() == s[r].lower():
                l += 1
                r -= 1
            else:
                return False
        return True

Complexity

• time: O(n)
• space: O(1)