[LeetCode] Valid Palindrome

문제

Given a string s, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

예제

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.

조건

Constraints:

• 1 <= s.length <= 2 * 105
• s consists only of printable ASCII characters.

답

풀이 1

class Solution:
    def isPalindrome(self, s: str) -> bool:
        s2 = ""
        for i in s:
            if i.isdigit():
                s2 += i
            elif i.isalpha():
                s2 += i.lower()

        if s2 == s2[::-1]:
            return True
        else:
            return False

풀이 2

class Solution:
    def isPalindrome(self, s: str) -> bool:
        s2 = ""
        for i in s:
            if i.isdigit():
                s2 += i
            elif i.isalpha():
                s2 += i.lower()

        for i in range(len(s2)//2):
            if s2[i]  != s2[-1-i]:
                return False
        else:
            return True