[Leetcode] Valid palindrome @ Python

Original title address: https://oj.leetcode.com/problems/valid-palindrome/

Test instructions

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

For example,
"A man, a plan, a canal: Panama"is a palindrome

"Radar" is a palindrome

"Rotator" is a palindrome
"race a car"is not a palindrome.

Note:
Are you consider that the string might is empty? This was a good question to ask during a interview.

For the purpose of this problem, we define empty string as valid palindrome.

Thinking 1: Using Python's list comprehension and the isalnum () function of string we can write a very short solution (original):

class Solution:     # @param s, a string    # @return A Boolean    def Ispalindrome (self, s):        NewS forinif  i.isalnum ()]         # return NewS = = News[::-1]        return News[:len (News)/2] = = news[(len (News) +1)/2:][::-1]

It is necessary to note that the last line of the program is odd for news length or even common to both

News[:len (News)/2] = = news[(len (News) +1)/2:][::-1]

Problem-Solving Ideas 2: Remove characters that are not letters, then convert to lowercase, then simple palindrome judgment.

classSolution:#@param s, a string    #@return A Boolean    defIspalindrome (self, s):ifs = ="':            returnTrueElse: STmp="'             forIinchRange (0, Len (s)):ifS[i] >='a'  andS[i] <='Z' orS[i] >='0'  andS[i] <='9' orS[i] >='A'  andS[i] <='Z': STmp+=S[i] STmp=Stmp.lower () forIinchRange (0, Len (STMP)/2):                ifStmp[i]! = Stmp[len (STMP)-1-i]:returnFalsereturnTrue

Reference acknowledgements:

[1]http://www.cnblogs.com/zuoyuan/p/3765882.html

[Leetcode] Valid palindrome @ Python