Valid Palindrome.py

# https://leetcode.com/problems/valid-palindrome/
# Hak Soo Kim
# 3/17/2022

class Solution(object):
    def isPalindrome(self, s):
        l, r = 0, len(s) - 1
        while l < r:
            while l < r and not s[l].isalnum():
                l += 1
            while l < r and not s[r].isalnum():
                r -= 1
            if s[l].lower() != s[r].lower():
                return False
            l += 1;
            r -= 1
        return True

        """
        :type s: str
        :rtype: bool
        """

# 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 characters include letters and numbers.
#
# Given a string s, return true if it is a palindrome, or false otherwise.
#
# Example 1:
#
# Input: s = "A man, a plan, a canal: Panama"
# Output: true
# Explanation: "amanaplanacanalpanama" is a palindrome.
# Example 2:
#
# Input: s = "race a car"
# Output: false
# Explanation: "raceacar" is not a palindrome.
# Example 3:
#
# Input: s = " "
# Output: true
# Explanation: s is an empty string "" after removing non-alphanumeric characters.
# Since an empty string reads the same forward and backward, it is a palindrome.
#
# Constraints:
#
# 1 <= s.length <= 2 * 105
# s consists only of printable ASCII characters.