5/9 每日一題

 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.
  
  
  
  class Solution:

      def isPalindrome(self, s: str) -> bool:

          import re

          new_s=re.sub(r'[^A-Za-z0-9]','',s).lower()  

  #這邊原本使用[^A-z]  會導致除了英文字母以外的字符也被加入其中,ex:_

          if new_s == new_s[-1::-1]:

              return True

          return False