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LeetCode125. Valid Palindrome

程序员文章站 2024-03-06 21:51:44
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Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Note: For the purpose of this problem, we define empty string as valid palindrome.

Example 1:

Input: "A man, a plan, a canal: Panama"
Output: true

Example 2:

Input: "race a car"
Output: false

<思路>python的isalnum()很好用。

           从字符串两端开始比较,如果不是字母则向下比较,直到遍历字符串。

class Solution(object):
    def isPalindrome(self, s):
        """
        :type s: str
        :rtype: bool
        """
        l=0
        r=len(s)-1
        s = s.lower()
                
        while l<r:  
            while r>l and not s[l].isalnum():
                l += 1
            while r>l and not s[r].isalnum():
                r -= 1
            if s[l] != s[r]:
                return False
            l += 1
            r -= 1
        return True