Leetcode 125. Valid Palindrome

Seawolf

1. Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.
   
2. 
   
3. Note: For the purpose of this problem, we define empty string as valid palindrome.
   
4. 
   
5. Example 1:
   
6. 
   
7. Input: "A man, a plan, a canal: Panama"
   
8. Output: true
   
9. Example 2:
   
10. 
    
11. Input: "race a car"
    
12. Output: false
    
13. 
    
14. 
    
15. Constraints:
    
16. 
    
17. s consists only of printable ASCII characters.

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1. class Solution:
   
2.     def isPalindrome(self, s: str) -> bool:
   
3.         copy = s[:]
   
4.         s = list(s.lower())
   
5.         start = 0
   
6.         end = len(s) - 1
   
7.         while start < end:
   
8.             while start < end and not (97 <= ord(s[start]) <= 122 or 48 <= ord(s[start]) <= 57):
   
9.                 start += 1
   
10.             while start < end and not (97 <= ord(s[end]) <= 122 or 48 <= ord(s[end]) <= 57):
    
11.                 end -= 1
    
12.             if s[start] == s[end]:
    
13.                 start += 1
    
14.                 end -= 1
    
15.             else:
    
16.                 return False
    
17.         return True

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