Python 3.2 palindrome

问题:

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

racecar

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")

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.

回答1:

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

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

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

This is the trick @LennartRegebro mentioned

回答2:

def is_palindrome(text):
    text = text.replace(' ', '')
    text = text.casefold()
    if list(text) == list(reversed(text)):
        return True
    else:
        return False

回答3:

Try this

word='malayalam'
print(word==word[::-1])

回答4:

The best way to check a word is palindrome or not in Python is as below:

var[::] == var[::-1]

But, it is very important to understand that Python creates a new copy of string when you do var[::-1] Python internally don't know if the reverse will result in same string or not. So, it's coded in a way where it creates a new copy of it. So, when you try var[::1] is var[::-1] you will get FALSE.

回答5:

Here is my solution.

S = input("Input a word: ")

def isPalindrome(S):
    for i in range(0, len(S)):
        if S[0 + i] == S[len(S) - 1]:
            return "True"
    else:
        return "False"
print(isPalindrome(S))

回答6:

Here's my solution:

def isPalindrome(S):
    l = len(S)-1
    for i in range(0,l):
        if S[i]!=S[l-i]:
            return False
    return True

回答7:

Another way of doing it using recursion is:

def isPalindrome(word):
  if len(word) <= 1: return True
  return (word[0] == word[-1]) and isPalindrome(word[1:-1])

回答8:

this is my solution S = input("Input a word: ")

def isPalindrome(S):
    for i in range(0, len(S)):
        if S[0 + i] == S[len(S) - 1]:
            return "True"
        else:
            return "False"
print(isPalindrome(S))