"Leetcode" 125-valid palindrome

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.
"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.

Tags: Pointers String

Solution 1:my Weak suolution, create a new string to input only alphanumeric

BOOLIspalindrome (strings) {if(S.empty ())return true; string:: Iterator Iter1=s.begin (), iter2=S.end (); stringNews;  for(; iter1!=iter2;iter1++){        if(Isalnum (*iter1)) News.push_back (ToLower (*iter1)); }    if(news.size () = =1)return true;  for(intI=0, J=news.size ()-1; i<j;i++,j--){        if(News[i]!=news[j])return false; }    return true;}

Solution 2:clean Code

    BOOLIspalindrome (strings) { for(inti =0, j = s.size ()-1; I < J; i++, j--) {//Move 2 pointers from each end until they collide             while(Isalnum (s[i]) = =false&& i < j) i++;//Increment left pointer if not alphanumeric             while(Isalnum (s[j]) = =false&& i < j) j--;//decrement right pointer if no alphanumeric            if(ToUpper (s[i])! = ToUpper (S[j]))return false;//Exit and return error if not match        }            return true; }

 

"Leetcode" 125-valid palindrome