LeetCode 125. Valid Palindrome
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.My Solution
class Solution:
def isPalindrome(self, s: str) -> bool:
s = s.lower() # 소문자로 만들어준다. If not, ball과 BALL을 다른 문자로 인식.
strs = collections.deque() # list보다 deque을 사용하는 것이 훨씬 빠르다.
for char in s:
if char.isalnum(): # is alphanumeric 함수로 알파벳 or 숫자인지 check!
strs.append(char)
s = ''.join(strs)
return s == s[::-1] # 문자열 뒤집어서 비교. slicing을 사용하는것이 가장 빠름.