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.
1 <= s.length <= 2 * 105 s consists only of printable ASCII characters.
class Solution:
def isPalindrome(self, s: str) -> bool:
# Get the pure string
filtered_s = ""
for char in s:
if char.isalnum():
filtered_s += char.lower()
# initialize two pointers
left = 0 # Initialize left pointer
right = len(filtered_s) - 1 # Initialize right pointer
# Check for palindrome
while left < right:
if filtered_s[left] != filtered_s[right]:
return False
left += 1
right -= 1
return True
simple strightforward solution. But since I didn't know that isalnum() functions existed the code looked more complex initially. USing python functions makes code to much more easier to read
Time and space complexity are both O(n)