125.valid-palindrome

Statement

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Metadata

Link: 验证回文串
Difficulty: Easy
Tag: 双指针 字符串

给定一个字符串，验证它是否是回文串，只考虑字母和数字字符，可以忽略字母的大小写。

说明：本题中，我们将空字符串定义为有效的回文串。

示例 1:

输入: "A man, a plan, a canal: Panama"
输出: true
解释："amanaplanacanalpanama" 是回文串

示例 2:

输入: "race a car"
输出: false
解释："raceacar" 不是回文串

提示：

1 <= s.length <= 2 * 10⁵
字符串 s 由 ASCII 字符组成

Metadata

Link: Valid Palindrome
Difficulty: Easy
Tag: Two Pointers String

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.

Solution

Python 3

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

最后更新: October 11, 2023