Python 3.2回文 [英] Python 3.2 palindrome

问题描述

我正在做一些python在线教程，但我被困在一个练习中:回文词是一个单词，其拼写与反向相同.例如，单词

I'm doing some python online tutorials, and I got stuck at an exercise:A palindrome is a word which is spelled the same forwards as backwards. For example, the word

赛车

是回文:第一个和最后一个字母相同(r)，第二个和倒数第二个字母相同(a)，依此类推.编写一个函数isPalindrome(S)，它以字符串S作为输入，如果字符串是回文，则返回True，否则返回False. 这些是我写的代码:

is a palindrome: the first and last letters are the same (r), the second and second-last letters are the same (a), etc. Write a function isPalindrome(S) which takes a string S as input, and returns True if the string is a palindrome, and False otherwise. These is the code I wrote :

  def isPalindrome(S):
      if S[0] == S[-1]
        return print("True")
      elif S[0] == S[-1] and S[1] == S[-2] :
        return print("True")
      else:
        return print("False")

但是，如果单词是例如,, sarcas ,,，则输出不正确.因此，我需要对我的代码进行修复，以使其适用于任何单词.

But, if the word is for example ,,sarcas,, , the output is incorect. So I need a fix to my code so it works for any word.

推荐答案

一种单行解决方案，但是O(n)和内存昂贵:

A one line solution but O(n) and memory expensive is :

def isPalindrome(word) : return word == word[::-1]

使用相同内存量的O(n/2)解决方案是:

A O(n/2) solution that uses the same amount of memory is:

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

这是@LennartRegebro提到的把戏

This is the trick @LennartRegebro mentioned

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