125

125. Valid Palindrome

We’re asked to return True or False if some input string, s, is a Valid Palindrome - after removing all non-alphanumeric characters and ignoring case. Pretty simple, we use Python’s filter() method and the str.islanum property to filter out all non-alphanumeric characters. Then we convert all characters to lowercase and check if the string is equal to its reverse.

The solution is as follows:

class Solution:
    def isPalindrome(self, s: str) -> bool:
        s = ''.join(filter(str.isalnum, s)).lower()
        return s == s[::-1]

_ Time Complexity:

O(n) - Where n is the size of s, we traverse the entire string.

_ Space Complexity:

O(n) - We store the sanitized string.