[Python] 예제 : 회문(Palindrom)

문제

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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.

 

 

 

 

출력 예

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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.

 

 

 

 

 

해석

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1. 문자열을 소문자로 변환. -> lower()
2. 공백 제거. -> replace(" ", "")
3. 영문자만 추출 -> list(filter(str.isalpha, String)
4. 리스트를 스트링으로 변환 "".join(list)
5. 문자열 뒤집기 -> Strig[::-1]

 

s1 = "".join(list(filter(str.isalpha, input("Enter the sentence").lower().replace(" ", ""))))
s2 = s1[::-1]

if s1 == s2 :
    print(" ""%s"" is a palindrome. " % s2)
elif s1 != s2 :
    print(" ""%s"" is not a palindrome. " % s2)