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Neetcode: Valid Palindrome
Instructions
Given a string s, return true if it is a palindrome, otherwise return false.
A palindrome is a string that reads the same forward and backward. It is also case-insensitive and ignores all non-alphanumeric characters.
Note: Alphanumeric characters consist of letters (A-Z, a-z) and numbers (0-9).
Example 1:
Input: s = "Was it a car or a cat I saw?"
Output: trueExplanation: After considering only alphanumerical characters we have "wasitacaroracatisaw", which is a palindrome.
Example 2:
Input: s = "tab a cat"
Output: falseExplanation: "tabacat" is not a palindrome.
Constraints:
1 <= s.length <= 1000sis made up of only printable ASCII characters.
Solutions
Python
import re
from pprint import pprint as pp
class Solution:
ALPHANUM_REGEX = r"[A-Za-z0-9]"
def isPalindrome(self, s: str) -> bool:
left_pointer = 0
right_pointer = len(s) - 1
while left_pointer <= right_pointer:
if not re.match(self.ALPHANUM_REGEX, s[left_pointer]):
left_pointer += 1
continue
if not re.match(self.ALPHANUM_REGEX, s[right_pointer]):
right_pointer -= 1
continue
if s[left_pointer].lower() != s[right_pointer].lower():
return False
left_pointer += 1
right_pointer -= 1
return True
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